#include<iostream> #include<string> #include<algorithm> #include<stack> using namespace std; //0:0000000000 //1:0123456789 //2:0246802468 //3:0369258147 //4:0482604826 //5:0505050505 //6:0628406284 //7:0741852963 //8:0864208642 //9:0987654321 int main() { int t; long long m, n; cin >> t; int arr[10][10] = { {0,0,0,0,0,0,0,0,0,0}, {0,1,2,3,4,5,6,7,8,9}, {0,2,4,6,8,0,2,4,6,8}, {0,3,6,9,2,5,8,1,4,7}, {0,4,8,2,6,0,4,8,2,6}, {0,5,0,5,0,5,0,5,0,5}, {0,6,2,8,4,0,6,2,8,4}, {0,7,4,1,8,5,2,9,6,3}, {0,8,6,4,2,0,8,6,4,2}, {0,9,8,7,6,5,4,3,2,1} }; int a[10] = { 0,45,40,45,40,25,40,45,40,45 }; while (t--) { cin >> n >> m; if (m > n) cout << 0 << endl; else if (m % 10 == 0) cout << 0 << endl; else { int temp = m % 10; long long num = n / m; long long temp1 = num / 10; long long temp2 = num % 10; long long sum = temp1 * a[temp]; for (int i = 0; i <= temp2; i++) sum += arr[temp][i]; cout << sum << endl; } } return 0; } |
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