30 lines
542 B
C++
30 lines
542 B
C++
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#include<bits/stdc++.h>
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using namespace std;
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using ll = long long;
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void solve()
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{
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int c4=0,c7=0;
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string s;
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cin>>s;
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for(int i=0; i<s.size(); ++i)
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{
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if(s[i]=='4') c4++;
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else if(s[i]=='7') c7++;
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}
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if(c4==0 && c7==0) cout<<"-1"<<endl;
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else if(c4>c7) cout<<"4"<<endl;
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else if(c7>c4) cout<<"7"<<endl;
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else if(c7==c4) cout<<"4"<<endl;
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}
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int main()
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{
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ios_base::sync_with_stdio(false);
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cin.tie(nullptr);
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int TC = 1;
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//cin >> TC;
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//cin.ignore();
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while (TC--) solve();
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}
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