#include<stdio.h>
unsigned long long sum[21],f[21];
int main()
{
     int i,t,n,m;
     f[0]=0;f[1]=0;f[2]=1;
     sum[0]=1;sum[1]=1;
     for(i=2;i<=20;i++)
     {
          sum[i]=sum[i-1]*i;
          if(i>=3)
          f[i]=(i-1)*(f[i-1]+f[i-2]);
     }
     scanf("%d",&t);
     while(t--)
     {
          scanf("%d%d",&n,&m);
          printf("%llu\n",sum[n]/sum[m]/sum[n-m]*f[m]);
     }
     return 0;
}