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

public class Solution {

    static long sumOfGroup(long k) {
        long som=0;
       
        long n=k*(k-1)+1;
        for(int i=0;i<k;i++)
        {
            som+=n;
            n+=2;
        }
        return som;
    }

    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();
    }
}