#include<stdio.h>
int main(){
    int n;
    long long result = 0;
    scanf("%d",&n);
    if(n<0){
        printf("Invalid input");
        return 0;
    }
    for(int i=1;i<=n;i++){
        long long fact = 1;
        for(int j=1;j<=i;j++){
            fact = fact * j;
        }
        if(i%2==1){
            result = result + fact;
    }
    else {
        result = result - fact;
    }
    }
    printf("%d",result);
}