using System;

using System.Collections.Generic;

public class Program

{

    public static void Main()

    {

        var a = new List<int>() { 1, 5, 7, 2, 3, 10 };

        a.Sort();

        Console.WriteLine(binarySearch(a, 1));

    }

    public static int binarySearch<T>(List<T> a, T x)

    {

        var result = a.BinarySearch(x);

        return result >= 0 ? result : -1;

    }

}