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 {
   public static void main(String[] args) {
      Scanner sc = new Scanner(System.in);
      
      String[] input = sc.nextLine().split(" ");
      int a = Integer.parseInt(input[0]);
      int b = Integer.parseInt(input[1]);
      
      System.out.println(gcd(a,b));
   }
   
   
   public static int gcd(int a, int b) {
      if (a % b == 0) {
         return b;
      } else {
         return gcd(b, a % b);
      }
   }
}