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

public class Solution {

    static long sumOfGroup(int k) {
        if(k==1)
            return 1;
        int l=k;
        long num=1;
        while(k>1)
        {
            num=num+(2*(k-1));
            k--;
        }
        
        long sum=0;
        for(int i=0;i<l;i++)
        {
            sum=sum+num;
            num=num+2;
        }
        return sum;
    }

    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();
    }
}