#include<stdio.h>
int main(void)
{
	int n,sum;
	scanf("%d",&n);
	if(n<=3) 
	{
		printf("0\n");
		//return;
	}
	else
	{
		sum=n*(n-1)*(n-2)*(n-3)/24;
		printf("%d\n",sum);
	}
}