Contest1210/J2.cpp

#include<bits/stdc++.h>
using namespace std;
int main()
{
    int n,sum=0,fac=1;
    cin>>n;
    for(int i=1;i<=n;i++)
    {
        fac*=i;
        sum+=fac;
    }
    cout<<sum<<endl;
    return 0;
}