using System;

public class Program

{

    public static void Main()

    {

        int number;

        int sum = 0;

        for (int i = 0; i < 5; i++)

        {

            do

            {

                Console.WriteLine("Please enter a valid number: ");

            } while (!int.TryParse(Console.ReadLine(), out number));

            sum += number;

        }

        Console.WriteLine("The sum is {0}", sum);

    }

}