func_code_string: #include <bits/stdc++.h>   using namespace std;   long long a, b, res = 1;   int main() {     cin >> a >> b;     if (b - (a + 1) > 20) {       cout << 0;       return 0;     }     for (long long i = a + 1; i <= b; i++) res = (res * (i % 10)) % 10;     cout << res;   }   