#include<iostream>
#include<cstring>
using namespace std;

//高精度加法:将b的内容加到a;
void add(int a[], int b[]) {
	for (int i = 1; i <= b[0]; i++){
		a[i] = a[i]+b[i];
		a[i + 1] += a[i]/10;
		a[i] %= 10;
	}
	if (a[a[0] + 1] > 0) a[0]++;
	return;
} 

//高精度乘法
void mul(int a[], int b) {
		for (int i = 1; i <= a[0]; i++) a[i] *= b;
		for (int i = 1; i <= a[0]; i++) {
			a[i + 1] += a[i] / 10;
			a[i] %= 10;
		}
		while (a[a[0]+1] > 0) {
			a[0]++;
			a[a[0] + 1] = a[a[0]] / 10;
			a[a[0]] %= 10;
		}
	}

int main() {
	int n;//阶乘最大的循环次数;
	int arr[200];//记录下n的高精度数组;
	int sum[200];//求和数组;
	memset(sum, 0, sizeof(sum));
	memset(arr, 0, sizeof(arr));
	cin >> n;
	arr[0] = 1;
	arr[1] = 1;
	sum[0] = 1;
	if (n == 0) cout << 0;
	else {
		if (n == 1)cout << 1;
		else {
			for (int i = 1; i <=n; i++) {
				mul(arr, i);//阶乘:数组a从1乘到n;

				add(sum, arr);//每次阶乘的结果都加起来
			}
			sum[0] = arr[0];
			for (int i = sum[0]; i > 0; i--) cout << sum[i];
		}
	}
}