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

public class Solution {
    static long firstElement(int k) {
        if (k ==1){
            return 1;
        } else {
            return k-1 + firstElement(k-1);
        }
    }
    static long sumOfGroup(int k) {
        /*long temp = 0;
        for (int j = 1; j<=k; j++){
            temp +=j;
        }*/

        //long firstElem = (k+k-1-1)*2+1;
        //System.out.println(firstElement(k));
        long firstElem = (firstElement(k)-1)*2+1;
        long count = firstElem;
        for (int i = 1; i < k; i++) {

            count += firstElem +i*2;
        }
        return count;
        
        
        
        
        
        
        
        
        
        // Return the sum of the elements of the k'th group.
    }

    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();
    }
}