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

public class Solution {
    
    static long convert(long k) {
        return (k * (k + 1)) / 2;
    } 
    
    static long sumOfGroup(int k) {
        if (k == 0) return 0;
        // Return the sum of the elements of the k'th group.
        long oddNum = convert(k) * 2 - 1;
        long sum = 0;
        for (int i = 0; i < k; i++) {
            sum += oddNum;
            oddNum -= 2;
        }
        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();
    }
}