#include <bits/stdc++.h>

using namespace std;

long sumOfGroup(long k) {
    long long limit = ((k*(k+1))-1);
    long sum = 0;
   // int j=0;
    for(long i=limit,j=0;j<k;i-=2,j++){
        sum += i;
    }
    return sum;
}

int main() {
    long k;
    cin >> k;
    long answer = sumOfGroup(k);
    cout << answer << endl;
    return 0;
}