using System;

using System.Collections;

​

public class Program {

    public static void Main() {

        IEnumerator coroutine = startCoroutine(sequence());

        while(coroutine.MoveNext()) {

            Console.WriteLine(coroutine.Current);

        }

    }

    public static IEnumerator startCoroutine(IEnumerator e) {

        while(e.MoveNext()) {

            if(e.Current != null && e.Current is IEnumerator) {

                IEnumerator next = startCoroutine((IEnumerator)(e.Current));

                while(next.MoveNext()) {

                    yield return next.Current;

                }

            } else {

                yield return e.Current;

            }

        }

    }

    public static IEnumerator sequence() {

        Console.WriteLine("1st iterate");

        yield return iterate(5);

        Console.WriteLine("Pause");

        yield return pause(5);

        Console.WriteLine("1st iterate");

        yield return iterate(5);

    }

    public static IEnumerator pause (int n) {

        for(int i = 0; i < n; i++) {

            yield return "pause " + i;

        }

    }

    public static IEnumerator iterate (int n) {

        for(int i = 0; i < n; i++) {

            yield return "iterate " + i;

        }

    }

}