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[]a=new long[10000000];
        int p=0;
         for(int i=1;i<10000000;i++)
    {
        if(i%2!=0)
        {
            a[p]=i;
            p++;
        }
    }
        int j=0;
        long sum=0;
        for(int i=1;i<k-1;i++)
        {
             j=j+(k-i);
        }
        for(int i=j+1;i<=j+k;i++)
        {
            sum+=a[i];
           // System.out.println(sum);
        }
        return sum;
        // Return the sum of the elements of the k'th group.
    }

    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();
    }
}