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 n = 1;
        
        for(int i=1;i<k;i++){
            n+=i*2;
        }
        long temp=0;
        for(int i=0;i<k;i++){
            temp+=n;
            n+=2;
        }
        return temp;
    }

    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();
    }
}