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: Accepted)

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

public class Main{
	public static int x;
	public static int y;
	public static int z;

	public static void main(String[] args) throws IOException {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		String[] strArr = br.readLine().split(" ");
		x= Integer.parseInt(strArr[0]);
		y = Integer.parseInt(strArr[1]);
		if(x > y){
			solve(x,y);
		}
		else{
			solve(y,x);
		}
		System.out.println(z);

	}

	public static void solve(int big,int small){
		z = big % small;
		if (z == 0){
			z = small;
		}
		else{
			solve(small,z);
		}

	}

}