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 d = k * (k-1) + 1;
        long s = 0;
        long groupe = k + k - 1;
        for(long i = d; i < d+groupe; i++){
            if(i%2 == 1){
                s += i;
            }
        }
        return s;
    }

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