#include <iostream>

using namespace std; long long massup[21];

long long C(int c, int m) { if(c-m < m) return C(c,c-m); if(m == 0) return 1;

if(m == 1) return c; return C(c,m-1) * (c-m+1) / m; } int main() { massup[1] = 0; massup[2] = 1; for(int i=3;i<21;i++) { massup[i] = (i-1) * (massup[i-2] + massup[i-1]); } //cout << massup[20] << endl; int num, total, mess; cin >> num; while(num--) { cin >> total >> mess; cout << C(total, mess) * massup[mess] << endl; } //system("pause"); }