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.Scanner;
class Main{
    public static void main(String[] args){
	int x,y,temp;
	
	Scanner scan = new Scanner(System.in);
	x = scan.nextInt();
	y = scan.nextInt();
	
      	if(1>x || x>1000000000){System.exit(0);}
	if(1>y || y>1000000000){System.exit(0);}
	
	if(x>=y){
	    while((temp = x%y) != 0){
		x = y;
		y = temp;
	    }
	    System.out.println(y);
	}
	else {
	    while((temp = y%x)!=0){
		y = x;
		x = temp;
	    }
	    System.out.println(x);
	}
    }
}