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

public class Solution{

    static long sumOfGroup(long k) {
        // Return the sum of the elements of the k'th group.
      long temp=k;
      long counter=k;
     
    long numofnums=0;
      while(temp!=0)
      {
          numofnums=numofnums+(temp-1);
          temp--;
          
          
      }
      long num=0;
      //return numofnums;
      while(counter!=0)
      {
         //int num=0;
         num=num+(2*(numofnums)+1);
         numofnums++;
         counter--;
      }
      return num;
    }

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