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

public class Solution {
    
    static int firstelement(int k){
        int first=0,firstelement=0;
        for(int i=1;i<k;i++){
            first += i;
        }
        for(int i=1;i<first;i++){
            firstelement=firstelement+2;
        }
        return firstelement+1;
    }

    static long sumOfGroup(int k) {
        int sum=0;
        int element = firstelement(k);
        for(int i=0;i<k;i++){
            element = element + 2;
            sum += element;
        }
        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();
    }
}