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 C# (judge verdict: Accepted)

using System;

class Program
{
	static void Main(string[] args)
	{
		string[] input = Console.ReadLine().Split(' ');

		int x = int.Parse(input[0]);
		int y = int.Parse(input[1]);

		Console.WriteLine(GetGCD(x, y));
	}

	static int GetGCD(int x, int y)
	{
		if (x < y)
		{
			int buf = x;
			x = y;
			y = buf;
		}

		return (x % y == 0) ? y : GetGCD(y, x % y);

	}
}