#include <bits/stdc++.h>   using namespace std;   int main() {     int cnt = 0;     int a;     string s;     cin >> s;     for (int i = 0; i < s.length(); i++) {       if (s[i] ==  4  || s[i] ==  7 ) {         cnt++;       }     }     if (cnt == 4 || cnt == 7) {       cout <<  YES ;     } else {       cout <<  NO ;     }     return 0;   }   