#include<stdio.h>

long long factorial(int num) {
    long long fact = 1;
    for (int i = 1; i <= num; i++) {
        fact *=i;
    }
    return fact;
}

int main() {
    int n;
    scanf("%d", &n);
    
    if (n < 0) {
        printf("Invalid input");
        return 0;
    }
    
    long long result = 0;
    
    for (int i = 1; i <= n; i++) {
        long long fact = factorial(i);
        
        if ( 1 % 2 == 1) {
            result += fact;
        }
        else {
            result -=fact;
        }
    }
    print("%lld",result);
    
    return 0;
}