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

public class Solution {

    static long sumOfGroup(int k) {
        // Return the sum of the elements of the k'th group.
        if (k == 1) return 1;
      long m = k - 1;
      long nums = m * (m + 1) / 2;
      
      
      long start = nums * 2 + 1;
      
      long sum = 0;
      for (long i = 0; i < k; i++) {
         sum += start;
         
         start += 2;
      }
      
      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();
    }
}