#include<bits/stdc++.h>using namespace std;long long js(long long);int n;long long sum=0;int main(){cin>>n;for(int i=1;1<=n;i++)sum+=js(i);cout<<sum<<endl;return 0;}long long js(int n){long long s=1;for(int i=1;i<=n;i++)s*=i;return s;}openjudge中‘求10000以內n的階乘’