func_code_string: #include <bits/stdc++.h>   using namespace std;   int main() {     int q;     cin >> q;     while (q--) {       long long n, m;       cin >> n >> m;       long long ans;       if (n < m) {         ans = 0;       } else if (n == m)         ans = m % 10;       else {         int d = m % 10;         int rem[10];         rem[0] = 0;         for (int i = 1; i < 10; ++i) {           rem[i] = (i * d) % 10 + rem[i - 1];         }         long long tot = n / m;         ans = rem[tot % 10] + (tot / 10) * rem[9];       }       cout << ans << endl;     }   }   