#include<stdio.h>
#include<stdlib.h>
int main()
{
    int M,N,num,n,m,a,b,t;
    m=1,n=1,a=1,b=1,t=N-1;
    while(scanf("%d%d",&M,&N)!=EOF){
    while(m<=(M-1)){
                  a=a*m;
                  m++;
                  }
    while(n<=(M-1)){
                  b=b*t;
                  t--;
                  n++;
                  }
    num=b/a;
    printf("%d",num);
    printf("\n");}
system("PAUSE");
return 0;
}