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;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.IO;


namespace StartFinish
{
    class Program
    {   
        static void Main(string[] args)
        {
            int[] xy = Console.ReadLine().Split(' ').Select(int.Parse).ToArray();
            int x = xy[0];
            int y = xy[1];
            int r = x % y;
            while (r != 0)
            {
                x = y;
                y = r;
                r = x % y;
            }
            Console.WriteLine(y);
        }

        

    }
}