func_code_string: #include <bits/stdc++.h>   using namespace std;   int main() {     long long int t, n, i, s, a1, b1, m;     cin >> t;     while (t--) {       cin >> n >> m;       if (n < m) {         cout <<  0 n ;         continue;       }       if (n == m)         cout << n % 10 <<   n ;       else {         long long int a[10] = {}, b[11] = {};         for (i = 1; i <= 10; i++) {           a[i - 1] = (m * i) % 10;           b[i] += a[i - 1] + b[i - 1];         }         a1 = n / m;         b1 = a1 % 10;         a1 = a1 / 10;         s = a1 * b[10] + b[b1];         cout << s <<   n ;       }     }     return 0;   }   