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

public class Test
{
    public static void Main()
    {
        IEnumerable<int> zeroToTen = Enumerable.Range(0, 10);
        IEnumerable<int> result = zeroToTen;
        for (int i = 0; i < 10_000; i++)
        {
            result = result.Concat(zeroToTen);
        }

        var sw = Stopwatch.StartNew();
        foreach (int i in result) { }
        Console.WriteLine(sw.Elapsed);
    }
}