static void Main(string[] args)
        {
            Console.Write("Enter three names separated by space: ");
            string line = Console.ReadLine();

            string[] names = line.Split();

            names[1] = names[1].ToCharArray()[0] + ".";

            foreach (var item in names)
            {
                Console.Write(item + " ");
            }
            Console.WriteLine();

            File.WriteAllText(@"D:\programirane\imena.txt", names[0] + " " + names[1] + " " + names[2]);
        }