#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: 1001
	User: wangchenyu
	Language: C++
	Result: Wrong Answer
****************************************************************/