题解

#include <bits/stdc++.h>
using namespace std;
int main(){
    int n ,sum = 1;
    cin >> n;
    for (int i = 1 ; i <= n ; i++)  //n! = 1 * 2 * 3 * ··· * (n - 1) * n
    sum *= i;  //sum乘以i，i从1一直增加到n
    cout << sum;
    return 0;
}