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

public class Solution {

    static BigInteger sumOfGroup(int k) {
        if(k == 1){
            return BigInteger.valueOf(1);
        }
        // Return the sum of the elements of the k'th group.
        
        BigInteger sum = BigInteger.valueOf(0);
        BigInteger start = BigInteger.valueOf(k);
        start = start.multiply(BigInteger.valueOf(k-1));
        start = start.add(BigInteger.valueOf(1));
        for(int i = 0; i < k; i++){
            
            sum = sum.add(start.add(BigInteger.valueOf(i * 2)));
        }
        return sum;
    }

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int k = in.nextInt();
        BigInteger answer = sumOfGroup(k);
        System.out.println(answer.toString());
        in.close();
    }
}