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.*;
class Main {
  public static void main(String args[]){
  //input
    Scanner sc = new Scanner(System.in);
    int a = sc.nextInt();
    int b = sc.nextInt();
    //output
        System.out.println(gcd(a,b));
  }
  //判定
  static int gcd(int x, int y){
    int tmp;
    if(x<y){
      tmp = x;
      y = tmp;
      x = y;
    }
    while(y>0){
      tmp = x%y;
      x = y;
      y = tmp;
    }
    return x;
  }
}