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

public class Solution {

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        long k = in.nextInt();
        long answer = sumOfGroup(k);
        System.out.println(answer);
        in.close();
    }

    public static long sumOfGroup(long n){
        int size = (int)n;
        long firstNum = n*(n-1) + 1;
        long[] series = new long[size];
        long finalSum = 0;
        series[0] = firstNum;

        for(int i=1; i<n; i++){
            series[i] = firstNum + 2;
            firstNum = series[i];
        }

        for(long i : series){
            finalSum = finalSum + i;
        }
        return finalSum;
    }
}