using System;

public class Program

{

    public void Main()

    {

        var input = "1234567890AB";

        var output = SplitNum(input, 2);

        Console.WriteLine(string.Join(":", output));

    }

    private string[] SplitNum(string str, int num)

    {

        var ret = new string[6];

        for (var i = 0; i < str.Length / num; ++i) {

            ret[i] = str.Substring(i * num, num);

        }

        return ret;

    }

}