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 input = new Scanner(System.in);
int x = input.nextInt();
int y = input.nextInt();
int out = helper(x,y);
System.out.println(out);
}

public static int helper(int x, int y){
if(y == 0){
return x;
} else if(x >= y){
return helper(y, x%y);
} else {
return 1;
}
}

}