using System;

​

public class Program

{

    public static void Main()

    {

        Console.WriteLine(is123Array(new int[]{}));

        //Console.WriteLine("Hello World");

    }

​

    public static int is123Array(int[] a)

    {

        int ret = 0;

        int count = 0;

        for (int i = 0, j = i + 1; i < a.Length && j < a.Length; i++, j++)

        {

            // for (int j = i; j >= i;j++ )

            //{

                if (a[i] == 1 && a[j] == 2 && a[j + 1] == 3)

                {

                    count++;

                }

            //}

        }

​

        if (a.Length / 3 == count)

            ret = 1;

        return ret;

    }

}