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

public class Solution {

    static long sumOfGroup(int k) {
        
        // Find starting position
        int startPos = 0;
        for (int i = 1; i < k; i++) startPos += i;
        
        // Ending position
        int endPos = startPos + k;
        
        // Build array
        int[] oddNumbers = new int[endPos];
        int currentNum = 1;
        for (int i = 0; i < endPos; i++) {
            oddNumbers[i] = currentNum;
            currentNum += 2;
        }
        
        long totalSum = 0;
        for (int i = startPos; i < endPos; i++) totalSum += oddNumbers[i];
        
        return totalSum;
    }

    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();
    }
}