#include <iostream>#include <algorithm>#include <cstdio>#define LL __int64using namespace std;LL N,M;LL myc(LL n,LL r){	LL sum=1;	for(LL i=1;i<=r;i++)	sum=sum*(n-r+i)/i;	return sum;}int main(){	while(scanf("%d%d",&N,&M),N||M){		LL ans=myc(N,M);		printf("%I64d things taken %I64d at a time is %I64d exactly.\n",N,M,ans);	}	return 0;}