using System;

using System.Linq;

public class Program

{

    public static void Main()

    {

        Console.WriteLine(string.Join(",", getCommonDivisor(new int[]{3500, 4000, 5000, 6000})));

        Console.WriteLine(string.Join(",", getCommonDivisor(new int[]{4000, 6000, 8000, 10000})));

        Console.WriteLine(GCD(12,36));

    }

    private static int GCD(int a, int b)

    {

        while (a != 0 && b != 0)

        {

            if (a > b)

                a %= b;

            else

                b %= a;

        }

​

        return a == 0 ? b : a;

    }

    static int getCommonDivisor(int[] arr)  {

        if (arr.Length < 2) return arr[0];

        var result = GCD(arr[0], arr[1]);

        for( var n=2; n<arr.Length; n++ )

            result = GCD(arr[n], result);

        return result;

    }

    /*

        var min = arr.Min();

        if (min == 0)

            return 0;

        for (int n = min; n > 1; n--) {

            var isGCD = arr.All( num => num % n == 0);

            //var isGCD = true;

            //for (int i = 0; i < arr.Length; i++) {

                //if (arr[i] % n > 0) {

                    //isGCD = false;

                    //break;

                //}

            //}

​

            if (isGCD){

                return n;

            }

        }

​

        return 1;

    }

    */

}