Problem:
Greatest Common Divisor

Write a program which finds the greatest common divisor of two natural numbers a and b

Input

a and b are given in a line sparated by a single space.

Output

Output the greatest common divisor of a and b.

Constrants

1 ≤ a, b ≤ 109

Hint

You can use the following observation:

For integers x and y, if x ≥ y, then gcd(x, y) = gcd(y, x%y)

Sample Input 1

54 20

Sample Output 1

2

Sample Input 2

147 105

Sample Output 2

21

Solution in JAVA (judge verdict: WA: Presentation Error)

import java.util.Scanner;

public class Main {
	public static void main(String args[]){
		Scanner scan = new Scanner (System.in);
		
		int x, y, tmp, rest;
		
		x = scan.nextInt();
		y = scan.nextInt();
		
		if(x < y){
			
			tmp = x;
			x = y;
			y = tmp;
			
		}
		
		for(;;){
			
			rest = x % y;
			x = y;
			y = rest;
			if(x % y == 0) break;
		}
		
		System.out.print(y);
	}
}