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CSharp · Console

/Program.cs

using System;
using System.Linq;
using System.Text.RegularExpressions;

public class Program
{
	public static void Main()
	{
		string input = "";
		int numCheck = 0;
		Regex whiteList = new Regex("^[1234567890]+$");
		do
		{
			numCheck = 0;
			Console.Write("Please input the two numbers you wish to use seperated by a space: ");
			input = Console.ReadLine();
			var numbers = input.Split(new []{' '}, StringSplitOptions.RemoveEmptyEntries);
			if (numbers.Length != 2 || !numbers.All(num => whiteList.IsMatch(num)))
			{
				Console.WriteLine("You entered " + input + " You did not enter two numbers seperated by a space, please try again.");
				numCheck = 1;
			}
		}
		while (numCheck == 1);
	}
}