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

public class Solution {

    static long sumOfGroup(int k) {
        // Return the sum of the elements of the k'th group.
        long sum=0L;
        int n=1;
        int i=0;
        int num[]= new int[100000000];
        while(n<=100000)
        {
            if(n%2!=0)
            {
               num[i]=n; 
                i++;
                n++;
            }
            else
            {
            n++;    
            }
            
        }
       
        int sum1=0;
        for(int f=1;f<=k;f++)
        {
            sum1+=f;
        }
        
     
        for(int t=1;t<=i;t++)
        {
            int group[] = new int[t];
            
              int h=sum1-k;
          
            for(int u=0;u<t;u++)
                {
                
                    group[u]=num[h];
                    h++;
                }
            
            if(t==k)
            {
                for(int j=0;j<group.length;j++)
                {
                    sum+=group[j];
                }
            }
            
            
        }
        
        
            
        
        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();
    }
}