calculate SUM(n) = 1 + 2 + 3 + … + n.

Input
The input will consist of a series of integers n, one integer per line.

Output
For each case, output SUM(n) in one line, followed by a blank line. You may assume the result will be in the range of 32-bit signed integer.

import java.util.Scanner;

class Main{
    private static Scanner scanner;
    public static void main(String[] args) {
        scanner = new Scanner(System.in);
        while (scanner.hasNext()) {
            int n = scanner.nextInt();
            int sum = 0;
            for(int i = 1;i <= n;i++){
                sum += i;
            }
            System.out.println(sum);
            System.out.println();
        }
    }
}