func_code_string: #include <bits/stdc++.h>   using namespace std;   ofstream outfile;   ifstream infile;   int main() {     infile.open( input.txt );     outfile.open( output.txt );     long long int a, b;     cin >> a >> b;     if (a > b) {       cout <<  0 n ;       return 0;     } else if (b - a <= 20) {       long long int digit = 1;       for (long long int i = a + 1; i <= b; ++i) {         digit = (digit * i) % 10;       }       cout << digit <<   n ;       return 0;     }     cout <<  0 n ;   }   