import java.io.*;
import java.util.*;
import java.text.*;
import java.math.*;
import java.util.regex.*;

public class Solution {

    static BigInteger sumOfGroup(long k) {
        // Return the sum of the elements of the k'th group.
        long t= (k*(k-1))+1;
        BigInteger sum= BigInteger.valueOf(t);
        BigInteger p;
        for(long i=2;i<=2*(k-1);i=i+2)
        {
            p=BigInteger.valueOf(t+i);
            sum=sum.add(p) ;
        }
        return sum;
        
    }

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        long k = in.nextLong();
        BigInteger answer = sumOfGroup(k);
        System.out.println(answer);
        in.close();
    }
}