func_code_string: #include <bits/stdc++.h>   using namespace std;   long long fastpower(long long power, long long base) {     if (power == 0) return (1 % 1000000007);     long long sum;     sum = fastpower(power / 2, base) % 1000000007;     sum = ((sum % 1000000007) * (sum % 1000000007)) % 1000000007;     if (power & 1) sum = ((sum % 1000000007) * (base % 1000000007)) % 1000000007;     return (sum % 1000000007);   }   int main() {     ios::sync_with_stdio(0), ios_base::sync_with_stdio(0), cin.tie(0),         cout.tie(0);     ;     string s;     long long k, sum = 0;     cin >> s >> k;     long long rn =         (fastpower((long long)s.size() * k, 2) - 1 + 1000000007) % 1000000007;     long long r =         (fastpower((long long)s.size(), 2) - 1 + 1000000007) % 1000000007;     long long d = fastpower(1000000007 - 2, r);     for (int i = 0; i < (int)s.size(); ++i) {       if (s[i] ==  0  || s[i] ==  5 ) {         long long a = fastpower(i, 2);         sum = (sum % 1000000007 + a * rn % 1000000007 * d % 1000000007) %               1000000007;       }     }     cout << sum <<   n ;     return 0;   }   