using System;
using System.Collections.Generic;

public class Test
{
        static void Main(string[] args) {
            var list = new List<Tuple<DateTime,int>>();
            list.Add(Tuple.Create(DateTime.Parse("1/29/2018"), 1));
            list.Add(Tuple.Create(DateTime.Parse("1/25/2018"), 2));
            list.Add(Tuple.Create(DateTime.Parse("1/20/2018"), 3));
            list.Add(Tuple.Create(DateTime.Parse("1/10/2018"), 4));
            list.Add(Tuple.Create(DateTime.Parse("1/3/2018"), 5));
            Console.WriteLine(~list.BinarySearch(Tuple.Create(DateTime.Parse("1/1/2018"), 0), TupleCompare.Instance)-1);
            Console.WriteLine(~list.BinarySearch(Tuple.Create(DateTime.Parse("1/5/2018"), 0), TupleCompare.Instance)-1);
            Console.WriteLine(~list.BinarySearch(Tuple.Create(DateTime.Parse("1/28/2018"), 0), TupleCompare.Instance)-1);
            Console.WriteLine(~list.BinarySearch(Tuple.Create(DateTime.Parse("2/1/2018"), 0), TupleCompare.Instance)-1);
        }

        class TupleCompare : IComparer<Tuple<DateTime,int>> {
            public static readonly TupleCompare Instance = new TupleCompare();
            public int Compare(Tuple<DateTime,int> x, Tuple<DateTime,int> y) {
                return -x.Item1.CompareTo(y.Item1);
            }
        }
}