using System;

using System.Threading.Tasks;

using System.Linq;

​

​

public class Program

{

    public static void Main() 

    {

        string strA = "1234567890";

string[] split = new string[strA.Length/2 + (strA.Length%2 == 0 ? 0 : 1)];

for (int i = 0; i < split.Length; i++)

{

    split[ i ] = strA.Substring(i * 2, i * 2 + 2 > strA.Length ? 1 : 2);

}

        split.ToList().ForEach(x => Console.WriteLine(x));

    }

}