---

using System.Collections;

internal class Program
{
    internal class MyEnumerator : IEnumerator
    {
        private Arr arr;

        public MyEnumerator(Arr arr)
        {
            this.arr = arr;
        }

        public object Current => throw new NotImplementedException();

        public bool MoveNext()
        {
            throw new NotImplementedException();
        }

        public void Reset()
        {
            throw new NotImplementedException();
        }
    }
    class Arr : IEnumerable
    {
        public IEnumerator GetEnumerator()
        {
            return new MyEnumerator(this);
        }
    }
    private static void Main(string[] args)
    {
        int[] ar = new int[] { 5, 4, 3, 2 };
        IEnumerable<int> ie = ar;
        foreach (int i in ie)
            Console.WriteLine(i);
    }
}