#include<iostream>
using namespace std;
int jie(int n)
{
int a = 1;
for (int i = 1; i <= n; i++)
a *= i;
return a;
}
int main()
{
int n;
cout << “请输入一个非负整数n” << endl;
while (cin >> n)
{
cout << (n == 0 ? 1 : n * jie(n - 1)) << endl;
cout<< “请输入一个非负整数n” << endl;
}
return 0;
}