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 sum = 0;
        long sum1 = 0;
        for(long i= 1;i<k;i++)
            sum = sum + i;
        sum = sum*2;
        long i = 0;
        while(i<k)
        {
            if(sum%2!=0)
            {
                sum1 = sum1 + sum;
                i++;
            }
        sum++;
        }
        return sum1;
    }

    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();
    }
}