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 st = ((k-1)*(2 + (k - 2)))/2;
        //System.out.println(st);
        long n = 1 + (st)*2;
        //System.out.println(n);
        long l = 1 + (st+k-1)*2;
        long res = ((k)*(2*n + ((k-1)*2) ))/2;
        return res;
    }

    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();
    }
}