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

public class Solution {

    static long sumOfGroup(int k) {
        long kElementsSum = 1;
        if (k > 2) {
            // Return the sum of the elements of the k'th group.
            // first find the sum of the k indexes
            // apply Gauss formula for finding sum of consecutive numbers -- (n / 2) * (first + last)
            int nextToLast = k - 1;
            long kIndexSum = (long) ((nextToLast / 2.0) * (1 + nextToLast));
            // find the first element
            long firstKelement = 2 * kIndexSum + 1;
            long currentElement = firstKelement;
            int consecElementsCounter = 1;
            kElementsSum = firstKelement;
            while (consecElementsCounter < k) {
                currentElement += 2;
                kElementsSum += currentElement;
                consecElementsCounter++;
            }
        } else if (k == 2) {
            kElementsSum = 8;
        }
        return kElementsSum;
    }

    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();
    }
}