CalculateGCD

using System;
class CalculateGCD
{
    // CONDITION:
    // Write a program that calculates the greatest common divisor (GCD) of given two integers a and b. Use the Euclidean algorithm (find it in Internet).

    static void Main()
    {
        int a = int.Parse(Console.ReadLine());
        int b = int.Parse(Console.ReadLine());
        int sum;

        if (a != 0 && b != 0)
        {
            if (a < b)
            {
                sum = b - a;
                a = a - sum - sum;
                if (a == 0)
                {
                    Console.WriteLine(sum);
                }
                else
                {
                    if ((b %= a) == 0)
                    {
                        Console.WriteLine(a);
                    }
                    else if ((a %= b) == 0)
                    {
                        Console.WriteLine(b);
                    }
                }
            }
            else if (a > b)
            {
                sum = a - b;
                b = b - sum - sum;
                if (b == 0)
                {
                    Console.WriteLine(sum);
                }
                else
                {
                    if ((a %= b) == 0)
                    {
                        Console.WriteLine(b);
                    }
                    else if ((b %= a) == 0)
                    {
                        Console.WriteLine(a);
                    }
                }
            }
        }

    }

}