using System;
using System.Collections.Generic;
using System.Linq;

public class Test
{
	public static void Main()
	{
		 foreach (var v in Split("abcdefghij"))
		 {
		 	Console.WriteLine(v);
		 }
	}
	static IEnumerable<string> Split(string str)
	{
	    while (str.Length > 0)
	    {
	        yield return new string(str.Take(3).ToArray());
	        str = new string(str.Skip(3).ToArray());
	    }
	}
}