#include<bits/stdc++.h>
using namespace std;

long long k,A,B;

int main()
{
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    cin>>k;
    A=(k*(k+1))/2;
    A=(A*2)-1;
    k--;
    B=(k*(k+1))/2;
    B=(B*2)-1;

   // cout<<A<<" "<<B<<endl;

    k=0;
    for(long long i=B+2;i<=A;i+=2)
    k+=i;
    cout<<k<<endl;
    return 0;
}