#include <iostream>
#include <cstring>
#include <cstdio>
#include <cmath>
using namespace std;
struct _vlint {
	static const int _size = 10010;
	int len, num[_size];
	_vlint(int a = 0) {
		len = 1;
		memset(num, 0, sizeof(num));
		while (a) num[len] = a % 10, a /= 10, len++;
		len--;
	}
	int &operator[](int a) {
		return num[a];
	}
	void flat(int a) {
		len = a;
		for (int i = 1; i <= len; i++)
			num[i + 1] += num[i] / 10, num[i] %= 10;
		while (!num[len]) len--;
	}
	void print() {
		for (int i = max(len, 1); i >= 1; i--)
			printf("%d", num[i]);
	}
};
_vlint operator+(_vlint a, _vlint b) {
	_vlint c;
    int len = max(a.len, b.len);
    for (int i = 1; i <= len; i++) c[i] += a[i] + b[i];
    c.flat(len + 1);
    return c;
}
_vlint operator*(_vlint a, int b) {
	_vlint c;
    int len = a.len;
    for (int i = 1; i <= len; i++) c[i] = a[i] * b;
    c.flat(len + 11);
    return c;
}
int main() {
    freopen("factorial.in", "r", stdin);
    freopen("factorial.out", "w", stdout);
    _vlint ans(0), fac(1);
    int n;
    scanf("%d", &n);
    for (int i = 1; i <= n; i++) {
    	fac = fac * i;
    	ans = ans + fac;
	}
	ans.print();
	return 0;
}