#include<iostream>

using namespace std;

long long fac(int x)
{
    if(x==0) return 1;
    else if(x==1) return 1;
    else return x*fac(x-1);
}

long long DiagonalIntersection(int n)
{
    return (fac(n))/(fac(n-4)*fac(4));
}

int main(void)
{
    int n;
    cin>>n;

    if(n<=3) cout<<0;
    else
    {
        cout<<DiagonalIntersection(n);
    }

    return 0;
}