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.*;

class Main{
  public static void main(String args[]){
  	Scanner sc = new Scanner(System.in);
    int x = sc.nextInt();
    int y = sc.nextInt();
    class Inner{
      int inner(int x,int y){
        if(y == 0){
          return x;
        }else{
          return inner(y,x%y);
        }
      }
    }
    Inner in = new Inner();
    System.out.println(in.inner(x,y));
  }
}