import java.util.*;
import java.lang.*;
import java.io.*;
import java.util.Scanner;
class Main {
public static void main
(String args
[]) {
int a1 = 2;
int d = 2;
int sum = 0;
Scanner scanner
= new Scanner
(System.
in); int n = scanner.nextInt();
sum = ((2*a1 + d*(n - 1))/2)*n;
}
}
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