极限压缩

#include <bits/stdc++.h>
using namespace std;const int N=100001;int n,a[N];int main(){int n;cin>>n;if(n==0){cout<<1;return 0;}a[1]=1;for(int i=2;i<=n;i++)a[i]=a[i-1]*i;cout<<a[n];return 0;}