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

public class Solution {

    static long sumOfGroup(int ki) {
        // Return the sum of the elements of the k'th group.
        long k = (long) ki;
        long firstOddIndex = (k*(k-1))/2 + 1;
      //  System.out.println(firstOddIndex);
        long firstOdd = 1 + (firstOddIndex-1)*2;
      //  System.out.println(firstOdd);
        long sum = 0;
        for(int i=0;i<k;i++) {
            sum += firstOdd + 2*i;
        }
        return sum;
    }

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