3.4

using System;

namespace _3._4
{
    class Program
    {
        static void Main(string[] args)
        {
            int[,] intArray =
            {
                { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 },
                { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 },
                { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 },
                { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 },
                { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 },
                { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 },
                { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 },
                { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 },
                { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 },
                { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 },
            };

            Random random = new Random();
            int bigest = int.MinValue;

            for (int i = 0; i < intArray.GetLength(0); i++)
            {
                intArray[i, 0] = random.Next(1, 1000);
                for (int j = 0; j < intArray.GetLength(1); j++)
                {
                    intArray[i, j] = random.Next(1, 1000);
                }
            }

            for (int i = 0; i < intArray.GetLength(0); i++)
            {
                for (int j = 0; j < intArray.GetLength(1); j++)
                {
                    Console.Write(intArray[i, j] + " ");
                    if (bigest < intArray[i, j])
                    {
                        bigest = intArray[i, j];
                    }
                }
                Console.WriteLine();
            }

            Console.WriteLine("\nСамое большое число массива: " + bigest + "\n");

            for (int i = 0; i < intArray.GetLength(0); i++)
            {
                for (int j = 0; j < intArray.GetLength(1); j++)
                {
                    if (bigest == intArray[i, j])
                    {
                        intArray[i, j] = 0;
                    }
                    Console.Write(intArray[i, j] + " ");
                }
                Console.WriteLine();
            }
        }
    }
}