#include <cstdio>
#include <cmath>
#include <cstring>
#include <iostream>
using namespace std;
int main() {
    
    int n;
    long long sum = 0,sum1 = 1;
    scanf("%d", &n);
    if(n == 0){
        printf("1");
        return 0;
    }
    for(int i = 1;i <= n;i++){
        for(int j = 1;j <= i;j++){
            sum1 *= j;
        }
        sum += sum1;
        sum1 = 1;
    }
    printf("%d", sum);
    return 0;
}