#include<stdio.h>

int main() {
    int n;
    scanf("%d",&n);
    
    if (n < 1) {
        printf("Invalid Input");
        return 0;
    }
    
    int fact = 1, sum = 0;
    
    for (int i = 1; i <= n; i++) {
        fact *= i;
        if (i % 2 == 1)
            sum += fact;
        else
            sum -= fact;
            
    }
    priontf("%d",sum);
    return 0;
}