C++ 代码
#include <iostream>
#include <string>
using namespace std;
int fact(int n){
int res = 1;
while(n){
res *= n--;
}
return res;
}
int fact1(int n){
if(n == 1)return 1;
return n * fact1(n - 1);
}
int main(){
int n;
cin >> n;
cout << fact1(n) << endl;
return 0;
}