safonovOplatit'

using System;
using System.Threading;

namespace ConsoleApplication1
{
    class Program
    {
        public static int[] A;
        public static int countElements = 1;
        public static int countThreads = 1;
        public static int subArrayLength;
        public static int sum = 0;
        public static object Locker = new object();

        static void Main(string[] args)
        {
            string userInput;
            Console.WriteLine("Размерность A: ");
            userInput = Console.ReadLine();

            if (int.TryParse(userInput,out countElements) == false || countElements <= 0)
            {
                countElements = 10;
                Console.WriteLine($"Не вводите буквы или значения <= 0. Количество элементов - {countElements}");
            }
            A = new int[countElements];
            FillArray(ref A);
            ViewArray(A);
            Console.WriteLine("\nКоличество потоков: ");
            userInput = Console.ReadLine();

            if (int.TryParse(userInput,out countThreads) == false || countThreads <= 0)
            {
                countThreads = 1;
                Console.WriteLine($"Не вводите буквы или значения <= 0. Количество потоков - {countThreads}");
            }

            if (countThreads > countElements)
                countThreads = countElements;
            subArrayLength = countElements / countThreads + 1;

            Thread[] flows = new Thread[countThreads];

            for (int i = 0; i < countThreads; i++)
            {
                PartArray partArray = new PartArray
                {
                    StartIndex = i * subArrayLength,
                    EndIndex = (i + 1) * subArrayLength
                };

                if (partArray.EndIndex > countElements)
                    partArray.EndIndex = countElements;
                flows[i] = new Thread(() => Sum(partArray));
                flows[i].Name = $"Поток №{i + 1}";
                flows[i].Start();
            }

            WaitFlows(flows);
            Console.WriteLine($"Результат: {sum}");
        }

        public static void WaitFlows(Thread[] threads)
        {
            for (int i = 0; i < threads.Length; i++)
            {
                Console.WriteLine($"{threads[i].Name} - on");
                threads[i].Join();
                Console.WriteLine($"{threads[i].Name} - off");
            }
        }

        public static void FillArray(ref int[] array)
        {
            Random random = new Random();

            for(int i = 0; i < array.Length; i++)
                array[i] = random.Next(countElements);
        }

        public static void ViewArray(int[] array)
        {
            foreach (int item in array)
                Console.Write($"{item} ");
        }

        public static void Sum(PartArray partArray)
        {
            int startIndex = partArray.StartIndex;
            int endIndex = partArray.EndIndex;

            for (int i = startIndex; i < endIndex; i++)
            {
                if (A[i] % 2 == 0)
                {
                    lock (Locker)
                    {
                        sum += A[i];
                    }
                }
            }
        }
    }

    public class PartArray
    {
        public int StartIndex;
        public int EndIndex;
    }
}