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: Wrong Answer)

import java.util.Scanner;
public class Main
{
    public static void main(String[] args)
    {
	Scanner In = new Scanner(System.in);

	int a,b,c;

	do
	    {
		a = In.nextInt();
		b = In.nextInt();
	    }while(1 >= a && a >= Math.pow(10,9) && 1 >= b && b >= Math.pow(10,9));

	a = a > b ? a:b; 
	b = a < b ? a:b;

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