#include<iostream>
using namespace std;

int main() {
	int n, doc = 0;
	int rets[50] = {0};
	cin>>n;
	if (n < 0 || n > 50) return 0;
	for (int number = 0; number < n; number++) {
		for (int numbers = n - 1; numbers > 0; numbers--) {
			rets[number] == 0 ? rets[number] = n : rets[number] *= numbers;
		}
		doc += rets[number];
	}
	cout<<doc;
	return 0;
} 

为什么全错红啊，得的数都对了QWQ