func_code_string: #include <bits/stdc++.h>   using namespace std;   using ll = int64_t;   using ull = uint64_t;   inline void solve() {}   int main() {     ios::sync_with_stdio(0);     cin.tie(0);     string s;     cin >> s;     int lucky = 0;     for (auto const &c : s) lucky += c ==  4  || c ==  7 ;     bool is_lucky = lucky > 0;     while (lucky) {       int x = lucky % 10;       if (!(x == 4 || x == 7)) is_lucky = false;       lucky /= 10;     }     cout << (is_lucky ?  YES  :  NO );     return 0;   }   