using System;
using System.Collections.Generic;
using System.Linq;
 
public class Test
{
	static IEnumerable<string> foo(IEnumerable<string> src, string meta, int n)
	{
		if (src.First().Length == n)
			return src;
		else
			return foo(meta.SelectMany(x => src.Select(y => y + x)), meta, n);
	}
	public static void Main()
	{
		// your code goes here
		foreach (string s in foo("ab".Select(x => x.ToString()), "ab", 5))
			Console.WriteLine(s);
	}
}

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