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

public class Solution {

    static long sumOfGroup(int k) {
        // Return the sum of the elements of the k'th group.
        long beg = 1L * k * (k - 1) / 2;
        beg *= 2;
        beg++;
        
        long sm = 0L;
        for(int i = 0; i < k; i++){
            sm += beg;
            beg += 2;
        }
        
        return sm;
    }

    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();
    }
}