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.util.*;

public class Main {
    int GCD(int a,int b){
		if(b>a){int x=a;a=b;b=x;}
		while (a%b!=0){
			int x=a;
			a=b;b=x%b;
		}
		return b;
	}
	public static void main(String[] args){
	    Scanner sc=new Scanner(System.in);
	    System.out.println(new Main().GCD(sc.nextInt(),sc.nextInt()));
	}
}