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 sum = 0;
        long grpFirstEl = k*(k-1) + 1;
   
        for(int i=0; i<k; i++){
            sum += grpFirstEl;
            grpFirstEl += 2;
        } 
        
        return sum;
    }

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