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: Time Limit Exceeded)

import java.util.Scanner;
public class Main {
    public static void main(String[] args) {
       int a,b;
       int gcd = 1;
       Scanner input = new Scanner(System.in);
      a = input.nextInt();
      b = input.nextInt();
      for(int i = 1;i<=a&&i<=b;i++)
      {
          if(a%i==0&&b%i==0)
          {
              gcd = i;  
          }
      }
      System.out.println(gcd);
    }  
}