CODEFORCES problem 110A Nearly Lucky Number

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#include <iostream>
#include <cstdio>
#include <cstring>
#include <string>
using namespace std;

int main()
 {
     string number;
     int count = 0;
     int i;
     cin >> number;
     for(i = 0; i < number.length(); i++){
         if(number[i] == '4' || number[i] == '7')
            count++;
     }
     if(count == 4 || count == 7)
         cout << "YES" << endl;
     else
         cout << "NO" << endl;

     return 0;
 }