using System;

​

public class Program

{

    public static void Main()

    {

        DateTime? dt = null;

        do

        {

            Console.WriteLine("Input date: (dd/MM/yyyy)");

            var input = Console.ReadLine();

            try

            {

                dt = DateTime.ParseExact(input, "dd/MM/yyyy", System.Globalization.CultureInfo.InvariantCulture);

            }

            catch(Exception ex)

            {

                Console.WriteLine(ex.Message);

            }

        } while (!dt.HasValue);

        Console.WriteLine(dt.Value.ToString("F"));

    }

}