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

public class Solution {
    
    static long countNumber(int k){
        long total = 0;
        for(int i=1; i<=k; i++)
            total += i;
        return total;
    }

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

    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();
    }
}