#include <bits/stdc++.h>
using namespace std;
int main(){
	int i,sum=0;
	cin>>i;
	for(int y=1;y<=i;y++){
		int i2=1;
		for(int g=1;g<=y;g++)i2*=g;
		sum+=i2;
	}
	cout<<sum;
	return 0;
}

/**************************************************************
	Problem: 1019
	User: zhouhongyi
	Language: C++
	Result: Accepted
	Time:22 ms
	Memory:2072 kb
****************************************************************/