diff --git a/Codes/1921 A - Square/1921A.cpp b/Codes/1921 A - Square/1921A.cpp
new file mode 100644
index 0000000..f7e7205
--- /dev/null
+++ b/Codes/1921 A - Square/1921A.cpp	
@@ -0,0 +1,79 @@
+#include<bits/stdc++.h>
+using namespace std;
+
+#define FAST_IO             (ios_base:: sync_with_stdio(false),cin.tie(NULL));
+
+#define int                 long long
+#define ll                  long long
+#define ull                 unsigned long long
+#define endl                '\n'
+#define ff                  first
+#define ss                  second
+#define pb                  push_back
+#define all(x)              x.begin(), x.end()
+#define sz(x)               (int)(x).size()
+
+#define yes                 cout<<"YES"<<endl
+#define no                  cout<<"NO"<<endl
+#define neg1                cout<<-1<<endl
+
+#define PI                  3.141592653589793238
+#define MIN                 INT_MIN
+#define MAX                 INT_MAX
+#define INF                 LONG_LONG_MAX
+#define MOD                 1000000007
+#define LLM                 1000000000000000007
+
+ll factorial(ll n)              { if(n==0) return 1; ll res = 1; for (ll i = 2; i <= n; i++) res = res * i; return res; }
+ll nPr(ll n, ll r)              { return factorial(n) / factorial(n - r); }
+ll nCr(ll n, ll r)              { return factorial(n) / (factorial(r) * factorial(n - r));}
+ll gcd(ll a, ll b)              { if (b == 0) return a; return gcd(b, a % b); }
+ll lcm(ll a, ll b)              { return (a * b) / gcd(a, b);}
+ull mypow(ull a, ull b)         { ull ans = 1; a%=MOD; while(b){ if (b&1) ans = (ans*a) % MOD; a = (a*a) % MOD; b >>= 1; } return ans; }
+bool isPrime(ll n)              { if(n <= 1) return false; for(ll i = 2; i*i <= n; i++) if(n % i == 0) return false; return true; }
+
+#ifndef ONLINE_JUDGE
+#define dbg(x) cerr << #x <<" "; _print(x); cerr << endl;
+#define dbgin(x) cerr << #x <<" "; _print(x); cerr << ";"<<endl;
+#else
+#define dbg(x)
+#define dbgin(x)
+#endif
+
+void _print(int t) {cerr << t;}void _print(string t) {cerr << t;}void _print(char t) {cerr << t;}
+void _print(long double t) {cerr << t;}void _print(double t) {cerr << t;}void _print(unsigned ll t) {cerr << t;}
+template <class T, class V> void _print(pair <T, V> p);
+template <class T> void _print(vector <T> v);template <class T> void _print(set <T> v);
+template <class T, class V> void _print(map <T, V> v);template <class T> void _print(multiset <T> v);
+template <class T, class V> void _print(pair <T, V> p) {cerr << "{"; _print(p.first); cerr << ","; _print(p.second); cerr << "}";}
+template <class T> void _print(vector <T> v) {cerr << "[ "; for (T i : v) {_print(i); cerr << " ";} cerr << "]";}
+template <class T> void _print(set <T> v) {cerr << "[ "; for (T i : v) {_print(i); cerr << " ";} cerr << "]";}
+template <class T> void _print(multiset <T> v) {cerr << "[ "; for (T i : v) {_print(i); cerr << " ";} cerr << "]";}
+template <class T> void _print(unordered_set <T> v) {cerr<<"[ "; for(T i : v) {_print(i); cerr<<" ";} cerr<<"]";}
+template <class T, class V> void _print(map <T, V> v) {cerr << "[ "; for (auto i : v) {_print(i); cerr << " ";} cerr << "]";}
+template <class T, class V> void _print(multimap <T, V> v) {cerr << "[ "; for (auto i : v) {_print(i); cerr << " ";} cerr << "]";} 
+template <class T, class V> void _print(unordered_map <T, V> v) {cerr << "[ "; for (auto i : v) {_print(i); cerr << " ";} cerr << "]";}
+/////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
+
+void solve()
+{
+    vector<pair<int,int>>v;
+    for(int i=0; i<4; ++i)
+    {
+        int x,y;
+        cin>>x>>y;
+        v.pb({x,y});
+    }
+    sort(all(v));
+    int diff=abs(v[0].ss-v[1].ss);
+    cout<<diff*diff<<endl;
+}
+
+int32_t main()
+{
+    FAST_IO;
+    int TC = 1;
+    cin >> TC;
+    while (TC--) 
+        solve();
+}
\ No newline at end of file
diff --git a/Codes/1921 B - Arranging Cats/1921B.cpp b/Codes/1921 B - Arranging Cats/1921B.cpp
new file mode 100644
index 0000000..67b4365
--- /dev/null
+++ b/Codes/1921 B - Arranging Cats/1921B.cpp	
@@ -0,0 +1,82 @@
+#include<bits/stdc++.h>
+using namespace std;
+
+#define FAST_IO             (ios_base:: sync_with_stdio(false),cin.tie(NULL));
+
+#define int                 long long
+#define ll                  long long
+#define ull                 unsigned long long
+#define endl                '\n'
+#define ff                  first
+#define ss                  second
+#define pb                  push_back
+#define all(x)              x.begin(), x.end()
+#define sz(x)               (int)(x).size()
+
+#define yes                 cout<<"YES"<<endl
+#define no                  cout<<"NO"<<endl
+#define neg1                cout<<-1<<endl
+
+#define PI                  3.141592653589793238
+#define MIN                 INT_MIN
+#define MAX                 INT_MAX
+#define INF                 LONG_LONG_MAX
+#define MOD                 1000000007
+#define LLM                 1000000000000000007
+
+ll factorial(ll n)              { if(n==0) return 1; ll res = 1; for (ll i = 2; i <= n; i++) res = res * i; return res; }
+ll nPr(ll n, ll r)              { return factorial(n) / factorial(n - r); }
+ll nCr(ll n, ll r)              { return factorial(n) / (factorial(r) * factorial(n - r));}
+ll gcd(ll a, ll b)              { if (b == 0) return a; return gcd(b, a % b); }
+ll lcm(ll a, ll b)              { return (a * b) / gcd(a, b);}
+ull mypow(ull a, ull b)         { ull ans = 1; a%=MOD; while(b){ if (b&1) ans = (ans*a) % MOD; a = (a*a) % MOD; b >>= 1; } return ans; }
+bool isPrime(ll n)              { if(n <= 1) return false; for(ll i = 2; i*i <= n; i++) if(n % i == 0) return false; return true; }
+
+#ifndef ONLINE_JUDGE
+#define dbg(x) cerr << #x <<" "; _print(x); cerr << endl;
+#define dbgin(x) cerr << #x <<" "; _print(x); cerr << ";"<<endl;
+#else
+#define dbg(x)
+#define dbgin(x)
+#endif
+
+void _print(int t) {cerr << t;}void _print(string t) {cerr << t;}void _print(char t) {cerr << t;}
+void _print(long double t) {cerr << t;}void _print(double t) {cerr << t;}void _print(unsigned ll t) {cerr << t;}
+template <class T, class V> void _print(pair <T, V> p);
+template <class T> void _print(vector <T> v);template <class T> void _print(set <T> v);
+template <class T, class V> void _print(map <T, V> v);template <class T> void _print(multiset <T> v);
+template <class T, class V> void _print(pair <T, V> p) {cerr << "{"; _print(p.first); cerr << ","; _print(p.second); cerr << "}";}
+template <class T> void _print(vector <T> v) {cerr << "[ "; for (T i : v) {_print(i); cerr << " ";} cerr << "]";}
+template <class T> void _print(set <T> v) {cerr << "[ "; for (T i : v) {_print(i); cerr << " ";} cerr << "]";}
+template <class T> void _print(multiset <T> v) {cerr << "[ "; for (T i : v) {_print(i); cerr << " ";} cerr << "]";}
+template <class T> void _print(unordered_set <T> v) {cerr<<"[ "; for(T i : v) {_print(i); cerr<<" ";} cerr<<"]";}
+template <class T, class V> void _print(map <T, V> v) {cerr << "[ "; for (auto i : v) {_print(i); cerr << " ";} cerr << "]";}
+template <class T, class V> void _print(multimap <T, V> v) {cerr << "[ "; for (auto i : v) {_print(i); cerr << " ";} cerr << "]";} 
+template <class T, class V> void _print(unordered_map <T, V> v) {cerr << "[ "; for (auto i : v) {_print(i); cerr << " ";} cerr << "]";}
+/////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
+
+void solve()
+{
+    int n;
+    string s,f;
+    cin>>n>>s>>f;
+    int x=0,y=0,m=0;
+    for(int i=0; i<n; ++i)
+    {
+        if(s[i]=='1')   x++;
+        if(f[i]=='1')   y++;
+        if(s[i]!=f[i])  m++;
+    }
+    int r=abs(x-y);
+    int ans=r+(m-r)/2;
+    cout<<ans<<endl;
+}
+
+int32_t main()
+{
+    FAST_IO;
+    int TC = 1;
+    cin >> TC;
+    while (TC--) 
+        solve();
+}
\ No newline at end of file
diff --git a/Codes/1921 C - Sending Messages/1921C.cpp b/Codes/1921 C - Sending Messages/1921C.cpp
new file mode 100644
index 0000000..04a9116
--- /dev/null
+++ b/Codes/1921 C - Sending Messages/1921C.cpp	
@@ -0,0 +1,85 @@
+#include<bits/stdc++.h>
+using namespace std;
+
+#define FAST_IO             (ios_base:: sync_with_stdio(false),cin.tie(NULL));
+
+#define int                 long long
+#define ll                  long long
+#define ull                 unsigned long long
+#define endl                '\n'
+#define ff                  first
+#define ss                  second
+#define pb                  push_back
+#define all(x)              x.begin(), x.end()
+#define sz(x)               (int)(x).size()
+
+#define yes                 cout<<"YES"<<endl
+#define no                  cout<<"NO"<<endl
+#define neg1                cout<<-1<<endl
+
+#define PI                  3.141592653589793238
+#define MIN                 INT_MIN
+#define MAX                 INT_MAX
+#define INF                 LONG_LONG_MAX
+#define MOD                 1000000007
+#define LLM                 1000000000000000007
+
+ll factorial(ll n)              { if(n==0) return 1; ll res = 1; for (ll i = 2; i <= n; i++) res = res * i; return res; }
+ll nPr(ll n, ll r)              { return factorial(n) / factorial(n - r); }
+ll nCr(ll n, ll r)              { return factorial(n) / (factorial(r) * factorial(n - r));}
+ll gcd(ll a, ll b)              { if (b == 0) return a; return gcd(b, a % b); }
+ll lcm(ll a, ll b)              { return (a * b) / gcd(a, b);}
+ull mypow(ull a, ull b)         { ull ans = 1; a%=MOD; while(b){ if (b&1) ans = (ans*a) % MOD; a = (a*a) % MOD; b >>= 1; } return ans; }
+bool isPrime(ll n)              { if(n <= 1) return false; for(ll i = 2; i*i <= n; i++) if(n % i == 0) return false; return true; }
+
+#ifndef ONLINE_JUDGE
+#define dbg(x) cerr << #x <<" "; _print(x); cerr << endl;
+#define dbgin(x) cerr << #x <<" "; _print(x); cerr << ";"<<endl;
+#else
+#define dbg(x)
+#define dbgin(x)
+#endif
+
+void _print(int t) {cerr << t;}void _print(string t) {cerr << t;}void _print(char t) {cerr << t;}
+void _print(long double t) {cerr << t;}void _print(double t) {cerr << t;}void _print(unsigned ll t) {cerr << t;}
+template <class T, class V> void _print(pair <T, V> p);
+template <class T> void _print(vector <T> v);template <class T> void _print(set <T> v);
+template <class T, class V> void _print(map <T, V> v);template <class T> void _print(multiset <T> v);
+template <class T, class V> void _print(pair <T, V> p) {cerr << "{"; _print(p.first); cerr << ","; _print(p.second); cerr << "}";}
+template <class T> void _print(vector <T> v) {cerr << "[ "; for (T i : v) {_print(i); cerr << " ";} cerr << "]";}
+template <class T> void _print(set <T> v) {cerr << "[ "; for (T i : v) {_print(i); cerr << " ";} cerr << "]";}
+template <class T> void _print(multiset <T> v) {cerr << "[ "; for (T i : v) {_print(i); cerr << " ";} cerr << "]";}
+template <class T> void _print(unordered_set <T> v) {cerr<<"[ "; for(T i : v) {_print(i); cerr<<" ";} cerr<<"]";}
+template <class T, class V> void _print(map <T, V> v) {cerr << "[ "; for (auto i : v) {_print(i); cerr << " ";} cerr << "]";}
+template <class T, class V> void _print(multimap <T, V> v) {cerr << "[ "; for (auto i : v) {_print(i); cerr << " ";} cerr << "]";} 
+template <class T, class V> void _print(unordered_map <T, V> v) {cerr << "[ "; for (auto i : v) {_print(i); cerr << " ";} cerr << "]";}
+/////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
+
+void solve()
+{
+    int n,f,a,b;
+    cin>>n>>f>>a>>b;
+    vector<int>v(n);
+    for(auto &i:v)  cin>>i;
+    v.insert(v.begin(),0);
+    for(int i=1; i<=n; ++i)
+    {
+        int x=(v[i]-v[i-1])*a;
+        f -= min(x,b);
+        if(f<=0)
+        {
+            no;
+            return;
+        }
+    }
+    yes;
+}
+
+int32_t main()
+{
+    FAST_IO;
+    int TC = 1;
+    cin >> TC;
+    while (TC--) 
+        solve();
+}
\ No newline at end of file
diff --git a/Readme.md b/Readme.md
index 8610841..8d30420 100644
--- a/Readme.md
+++ b/Readme.md
@@ -240,7 +240,10 @@ This repository contains my solutions of Codeforces problems. They are in C++ la
 | 228 | 1919 A | Wallet Exchange | [Question](https://codeforces.com/problemset/problem/1919/A) | [Solution](https://github.com/ShazidMashrafi/Codeforces-Solutions/tree/master/Codes/1919%20A%20-%20Wallet%20Exchange)
 | 229 | 1919 B | Plus-Minus Split | [Question](https://codeforces.com/problemset/problem/1919/B) | [Solution](https://github.com/ShazidMashrafi/Codeforces-Solutions/tree/master/Codes/1919%20B%20-%20Plus-Minus%20Split)
 | 230 | 1920 A | Satisfying Constraints | [Question](https://codeforces.com/problemset/problem/1920/A) | [Solution](https://github.com/ShazidMashrafi/Codeforces-Solutions/tree/master/Codes/1920%20A%20-%20Satisfying%20Constraints)
-| 231 | 19020 B | Summation Game | [Question](https://codeforces.com/problemset/problem/19020/B) | [Solution](https://github.com/ShazidMashrafi/Codeforces-Solutions/tree/master/Codes/19020%20B%20-%20Summation%20Game)
+| 231 | 1921 A | Square | [Question](https://codeforces.com/problemset/problem/1921/A) | [Solution](https://github.com/ShazidMashrafi/Codeforces-Solutions/tree/master/Codes/1921%20A%20-%20Square)
+| 232 | 1921 B | Arranging Cats | [Question](https://codeforces.com/problemset/problem/1921/B) | [Solution](https://github.com/ShazidMashrafi/Codeforces-Solutions/tree/master/Codes/1921%20B%20-%20Arranging%20Cats)
+| 233 | 1921 C | Sending Messages | [Question](https://codeforces.com/problemset/problem/1921/C) | [Solution](https://github.com/ShazidMashrafi/Codeforces-Solutions/tree/master/Codes/1921%20C%20-%20Sending%20Messages)
+| 234 | 19020 B | Summation Game | [Question](https://codeforces.com/problemset/problem/19020/B) | [Solution](https://github.com/ShazidMashrafi/Codeforces-Solutions/tree/master/Codes/19020%20B%20-%20Summation%20Game)