include<iostream>

using namespace std;
int main()
{
long long p ;
cin >> p;
while(p)
{
long long n , m;
cin >> n >> m;
long long z = n - m;
long long n1=1, z1=1;
for (long long i = z,j=n; i > 0; i--,j--)
{
n1 *= j;

}
for (long long j = z; j > 0; j--)
{
    z1 *= j;
}
if (n == m)
    n1 = 1;
else
    n1 = n1 / z1;
long long c[100] = { 0,0,1 };
for (long long i = 3; i <= 25 ; i++)
    c[i] = (i-1)*(c[i-1]+c[i-2]);


cout << c[m] * n1<<endl;
p--;
}

}