An inefficient version of range-merge exam

RangeMerge.cs

/*
 * Input example: 1,2,8-20,15-200
 * Output: 1,2,8-200
 */

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

namespace Fold
{
	internal class Program
	{
		public static void Main(string[] args)
		{
			while (true)
			{
				var ranges = NormalizeRange(ReadRangeSorted());
				var enumerable = ranges as Tuple<int, int>[] ?? ranges.ToArray();
				if (!enumerable.Any())
					break;
				
				PrintRanges(enumerable);
			}
			
			Console.WriteLine("Until next time...");
		}

		private static IEnumerable<Tuple<int, int>> NormalizeRange(IEnumerable<Tuple<int, int>> ranges)
		{
			var enumerable = ranges as Tuple<int, int>[] ?? ranges.ToArray();
			if (!enumerable.Any())
				return new List<Tuple<int, int>>();

			return enumerable.Aggregate(new [] { enumerable.First() },
				(prod, next) =>
				{
					var src = prod.Last();
					if (next.Item1 >= src.Item1 && next.Item1 <= src.Item2)
					{
						return prod.TakeWhile((o, i) => i < prod.Length - 1).Concat(
							new [] { Tuple.Create(src.Item1, Math.Max(src.Item2, next.Item2)) }).ToArray();
					}

					return prod.Concat(new [] { next }).ToArray();
				}
			);
		}

		private static IEnumerable<Tuple<int, int>> ReadRangeSorted()
		{
			return ReadRange()
				.Select(t => t.Item1 <= t.Item2 ? t : Tuple.Create(t.Item2, t.Item1))
				.OrderBy(t => t.Item1);
		}
		
		private static IEnumerable<Tuple<int, int>> ReadRange()
		{
			Console.Write(">> ");
			var line = Console.ReadLine();
			if (string.IsNullOrEmpty(line))
				return new List<Tuple<int, int>>();

			var ranges = line.Split(',').Select(s => s.Trim()).Where(s => !string.IsNullOrEmpty(s))
				.Select(s =>
				{
					var r = s.Split('-');
					if (r.Length == 2)
						return Tuple.Create(int.Parse(r[0]), int.Parse(r[1]));

					var val = int.Parse(r[0]);
					return Tuple.Create(val, val);
				});

			return ranges.ToList();
		}

		private static void PrintRanges(IEnumerable<Tuple<int, int>> ranges)
		{
			var sranges = ranges.Select(range => range.Item1 == range.Item2
				? Convert.ToString(range.Item1)
				: string.Format($"{range.Item1}-{range.Item2}"));
			Console.WriteLine(string.Join(",", sranges));
		}
	}
}