#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++) {
        if (i % 2 == 1) {
            result += factorial(i);
        } else {
            
            result -= factorial(i)
        }
    }

    printf("%lld", result);
    return 0;
}