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: Runtime Error)

import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		Scanner number = new Scanner(System.in);
		int a  = number.nextInt();
		int b  = number.nextInt();
		int c;

		if(a < b) {
			c = a;
			a = b;
			b = c;
		}
		do {
			c = b;
			b = a % b;
			a = c;
		}while(a % b != 0);
		System.out.println(b);
	}
}