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

public class Solution {

    static long sumOfGroup(int k) {
        long[] dp = new long[k+1];
        dp[1] = 1;
        for(int i = 2; i<=k; i++) dp[i] = dp[i-1]+2*(i-1);
        long ans = 0;
        for(int i = 0; i<k; i++) ans+=dp[k]+i*2;
        return ans;
    }

    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();
    }
}