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

public class Solution {

    static long sumOfGroup(int k) {
        if (k == 1) return k;
        long first = 3;
        for (int i = 4, cnt = k; cnt > 2; i+=2, cnt--) {
            first += i;
        }

        long sum = 0;
        for (long i = first, cnt = 0; cnt < k; cnt++, i += 2) {
            sum += i;
        }

        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();
    }
}