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: Wrong Answer)

import java.util.Scanner;

public class Main{
  public static void main(String args[]) {
    Scanner stdln = new Scanner(System.in);
    String str = stdln.nextLine();
    String array[] = str.split("");
    int i = 0;
    while(i < array.length){
      if(array[i].equals("B")) {
        if(i > 0) {
          array[i] = null;
          int x = i;
          while(array[x] == null){
            x--;
            if(x == 0) break;
          }
          array[x] = null;
        }else{array[i] = null;}
      }
      i++;
    }
    StringBuilder buf = new StringBuilder();
    String s = null;
    int j = 0;
    while(j < array.length){
      if (array[j] != null) {
        buf.append(array[j]);
        j++;
      }else j++;
    }
    s = new String(buf);
    System.out.println(s);
  }
}