Мутанты

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ConsoleApp17
{
    class Program
    {
        static int BinSearch(int[] N, int key)
        {
            int l = -1, r = N.Length, m = 0;
            int counter = 0;
            while (l < r - 1)
            {
                m = (l + r) / 2;
                if (N[m] < key)
                    l = m;
                else
                    r = m;
            }

            if (r == N.Length)
                return -1;
            else if (N[r] == key)
            {
                N[r] = -1;
                counter++;
            }
            else
                return -1;
        }

        static void Main(string[] args)
        {
            int n = Convert.ToInt32(Console.ReadLine());
            int[] N = Console.ReadLine().Split(' ').Select(e => Convert.ToInt32(e)).ToArray();
            int m = Convert.ToInt32(Console.ReadLine());
            int[] M = Console.ReadLine().Split(' ').Select(e => Convert.ToInt32(e)).ToArray();

            for (int i = 0; i < m; i++)
                BinSearch(N, M[i]);

        }
    }
}