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.*;
import java.util.Arrays;
import java.util.Scanner;

class Main{
	public static void main(String[] args) throws IOException{
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		String[] line = (br.readLine()).split(" ");
		int a = Integer.parseInt(line[0]);
		int b = Integer.parseInt(line[1]);
		int x,y;
		if (a>b) {
			x = a;
			y = b;
		}else{
			x = b;
			y = a;
		}
		int work;
		while(x%y != 0) {
			work = y;
			y = x%y;
			x = work;
		}
		System.out.println(y);
	}
}