#include <cstdlib>
#include <cstdio>
#include <algorithm>
#include <cstring>

int n;
unsigned long long ans;

int main()
{
	scanf("%d",&n);
	ans = n*(n-1);
	ans /= 2;
	ans *= (n-2);
	ans /= 3;
	ans *= (n-3);
	ans /= 4;
	printf("%lld",ans);
	return 0;
}