func_code_string: #include <bits/stdc++.h>   using namespace std;   unsigned long long tcc, n, m;   int main() {     scanf( %lld , &tcc);     while (tcc--) {       scanf( %lld %lld , &n, &m);       unsigned long long sum = 0, m2 = m, t = 10;       while (t-- && m2 <= n) {         sum += m2 % 10;         m2 += m;       }       m2 = m * 10;       t = n / m2;       sum *= t;       n -= m2 * t;       m2 = m;       while (m2 <= n) {         sum += m2 % 10;         m2 += m;       }       printf( %lld n , sum);     }     return 0;   }   