Codeforces-SolutionsA/Codes/158 B - Taxi/158B.cpp

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2023-07-19 04:14:56 +08:00
#include<bits/stdc++.h>
using namespace std;
using ll = long long;
void solve()
{
int n;
cin>>n;
int ct1=0, ct2=0, ct3=0, ct4=0;
for(int i=0; i<n; ++i)
{
int x;
cin>>x;
if(x==1)
ct1++;
else if(x==2)
ct2++;
else if(x==3)
ct3++;
else
ct4++;
}
int taxi=ct4;
if(ct2>1)
{
taxi=taxi+ct2/2;
ct2=ct2%2;
}
while(ct3>0 && ct1>0)
{
taxi++;
ct3--;
ct1--;
}
if(ct3>0)
taxi=taxi+ct3;
if(ct1>0 && ct2>0)
{
taxi++;
ct2--;
ct1=ct1-2;
}
while(ct2>0)
{
taxi++;
ct2--;
}
while(ct1>0)
{
taxi++;
ct1=ct1-4;
}
cout<<taxi<<endl;
}
int main()
{
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
int TC = 1;
//cin >> TC;
//cin.ignore();
while (TC--) solve();
}