func_code_string: #include <bits/stdc++.h>   using namespace std;   int main() {     int t;     cin >> t;     while (t--) {       long long n, m;       cin >> n >> m;       long long sum = 0, cyl = 0;       long long k = (n / m);       for (int i = 1; i <= 10; ++i) {         cyl += (m * i) % 10;       }       sum = (k / 10) * cyl;       cyl = 0;       for (int i = 1; i <= k % 10; ++i) {         cyl += m * (i) % 10;       }       cout << sum + cyl << endl;     }     return 0;   }   