#include <bits/stdc++.h>

using namespace std;
long long jc(int x) {
	
	long long ret = 1;
	for (int i = 1;i <= x; i++) {
		ret = ret * i;
	}
	return ret;
}
int main () {
	int n;
	cin >> n;
	
	int sum = 0;
	for (int i = 1;i <= n;i++) {
		long long ret1 = jc(i);
		
		sum +=  ret1;
	}
	printf("%d",sum);
	return 0;
}