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.Scanner;

public class Main{
    public static void main(String[] args){
	Scanner sc = new Scanner(System.in);
	int n1 = sc.nextInt();
	int n2 = sc.nextInt();
	System.out.println(euc(n1,n2));
    }
    private static int euc(int n1, int n2){
	if(n1 < n2) return euc(n2,n1);
	if(n2 == 0) return n1;
	return euc(n2,n1%n2);
    }
}