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.
        int n=0;
        for(int i=k;i>1;i--)
        {
            n+=i;
        }
        int p[]=new int [n+1];
        int m=1;
        for(int j=0;j<n+1;j++){
            p[j]=m;
            m+=2;
        }
        long res=0;
        int f=n-(k-1);
        for(int g=f;g<(f+k);g++){
            res+=p[g];
        }
        return res;
    }

    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();
    }
}