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#include <bits/stdc++.h>
 
using namespace std;
 
int main()
{
    unsigned long long int n; cin >> n;
    int tLN = 0;
    for (int i = 0; i < to_string(n).length(); i++)
    {
        if (n[i] == 4 || n[i] == 7)
        {
            tLN += 1;
        }
    }
    if (tLN == 4 || tLN == 7)
    {
        cout << "YES" << endl;
        return 0;
    }
    cout << "NO" << endl;
    return 0;
}

prog.cpp: In function ‘int main()’:
prog.cpp:11:16: error: invalid types ‘long long unsigned int[int]’ for array subscript
         if (n[i] == 4 || n[i] == 7)
                ^
prog.cpp:11:29: error: invalid types ‘long long unsigned int[int]’ for array subscript
         if (n[i] == 4 || n[i] == 7)
                             ^

Standard output is empty