#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);
}