func_code_string: #include <bits/stdc++.h>   using namespace std;   int main() {     long long k4, k7, i, l;     char s[100];     long long n;     gets(s);     l = strlen(s);     k4 = 0;     k7 = 0;     for (i = 0; i < l; i++) {       if (s[i] ==  4 ) k4++;       if (s[i] ==  7 ) k7++;     }     if (k4 == 0 && k7 == 0)       cout << -1;     else if (k7 > k4)       cout << 7;     else       cout << 4;     return 0;   }   