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.io.*;

public class Main {
  public static void main(String[] args) {
    try {
      BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
      String input = new String(in.readLine());
      String[] inputArr = input.split(" ");
      int x = Integer.parseInt(inputArr[0]);
      int y = Integer.parseInt(inputArr[1]);
      if ( x > y ) {
        int tmp = x;
        x = y;
        y = tmp;
       }
       while ( x > 0 ) {
         int tmp = x;
         x = y % x;
         y = tmp;
       }
       System.out.println(y);
    } catch( IOException e ) {
    }
  }
}