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 1;

        long start = 0;
        for (int i = 1; i < k; i++){
            start += 2 * i;
        }
        start ++;
        long finish = start + 2 * (k - 1);
        long sum = 0;
        for(long m = start; m <= finish; m += 2){
            sum += m;
        }
        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();
    }
}