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