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 JavaScript (node.js v5.12) (judge verdict: Wrong Answer)

function Main(input) {
  const data = input.split("");
  var ans = [];
  for (var i = 0; i < data.length; i++) {
    if (data[i] === "1") {
      ans.push("1");
    } else if (data[i] === "0") {
      ans.push("0");
    } else if (data[i] === "B") {
      if (ans.length > 0) {
        ans.pop();
      } else {
        continue;
      }
    }
  }
  console.log(ans.join(""));
}
 
Main(require("fs").readFileSync("/dev/stdin", "utf8"));