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.*;
import java.io.*;
import static java.util.Arrays.*;
import static java.util.Collections.*;
import static java.lang.Math.*;


public class Main {

	public static void main(String[] args) {
		// TODO ?????????????????????????????????????????????
		int a,b,c;
        Scanner scan=new Scanner(System.in);
        a=scan.nextInt();
        b=scan.nextInt();
        while(a!=0)
        {
        	if(a>=b)
            {
            	a=a%b;
            }
        	if(b>a)
        	{
        		c=b;
        		b=a;
        		a=c;
        		a=a%b;
        	}
        }
        System.out.println(b);
        
	}

}