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

public class Solution {

  static long sumOfGroup(int k) {
    int sum = 0, i = 1, j = 0, g = 1;
    while (g != k) {
      for (j = 0; j < g; j++) {
        i += 2;
      }
      g++;
    }
    for (int m = 0; m < k; m++) {
      sum += i;
      i += 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();
  }
}