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 {
private static Scanner scanner;

public static void main(String args[])
{
	scanner = new Scanner(System.in);
	int a = scanner.nextInt(),b = scanner.nextInt();
	if(a < b) {
		int tmp = a;
		a = b;
		b = tmp;
	}
	while(a%b != 0) {
		int c = a%b;
		a = b;
		b = c;
	}
	System.out.println(b);
}
}