using System;
using System.Linq;

public class Test
{
	public static void Main()
	{
	    string cardNumber = "1234567890123456";
        var subStrings = Enumerable.Range(0, 4).Select(n => cardNumber.Substring(n * 4, 4));
        var result = String.Join("-", subStrings);
        Console.WriteLine(result);
	}
}