#include <iostream>
using namespace std;

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