Problem:
Score : 100 points

Problem Statement

There are N children in AtCoder Kindergarten. Mr. Evi will arrange the children in a line, then give 1 candy to the first child in the line, 2 candies to the second child, ..., N candies to the N-th child. How many candies will be necessary in total?

Constraints

1≦N≦100

Input

The input is given from Standard Input in the following format:

N

Output

Print the necessary number of candies in total.

Sample Input 1

3

Sample Output 1

6

The answer is 1+2+3=6.

Sample Input 2

10

Sample Output 2

55

The sum of the integers from 1 to 10 is 55.

Sample Input 3

1

Sample Output 3

1

Only one child. The answer is 1 in this case.

Solution in Java8 (OpenJDK 1.8.0) (judge verdict: Accepted)

import java.util.*;


public class Main {
	
	Scanner cin = new Scanner(System.in);
	
	public static void main(String[] args) {
		new Main().run(); 
	}
	
	public void run() {		
		
		/*input*/
		
		int n = cin.nextInt();
		
		/*start*/
		
		long res = (1 + n) * n / 2;
		
		/*finish*/
		System.out.println(res);
	}
}