#include <iostream>

using namespace std;

int main(){
	int i,n,j,c=1,x=0;
	cin>>n;
	for(i=1;i<=n;i++){
		for(j=1;j<=i;j++){
			c=c*j;
		}x=x+c;
		c=1;
	}cout<<x<<endl;
}
/**************************************************************
	Problem: 1019
	User: admin
	Language: C++
	Result: Accepted
	Time:8 ms
	Memory:2072 kb
****************************************************************/