组合数计算

#include<bits/stdc++.h>
using namespace std;
#define ll long long
ll c(int n,int m){
	if(m<n-m) m=n-m;
	ll ans=1;
	for(int i=n;i>=m+1;i--)
	  ans*=i;
	  for(int j=1;j<=n-m;j++)ans/=j;
	  return ans;
}
int main(){
	int n,m;
	while(cin>>n>>m){
		cout<<c(n,m)<<endl;
	}
	return 0;
}