#include<iostream>
using namespace std;
long fac(int n)//求 N的阶乘
{
int j = 1;
while ( n > 0 )
{
j = j * n;
n--;
}
return j;
}
int main()
{
int m,n,C_mn;
cout << "请输入m,n的值" << endl;
cin >> m >> n;
C_mn = fac(m)/( fac(n)*( fac(m-n) ) );
cout << "所求组合数为" << C_mn << endl;
return 0;
}
