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 x = sc.nextInt();
		int y = sc.nextInt();
		System.out.println(getGCD(x, y));
		sc.close();
	}

	public static int getGCD(int a, int b) { // ユークリッドの互除法
		if(a < b) {
			int t = a;
			a = b;
			b = t;
		}
		int c = a % b;
		if(c == 0) {
			return b;
		}else {
			return getGCD(b, c);
		}
	}
}