Open url in Webbrowser without www. in C#

I have a program where you can enter a word and it opens the wikipedia article.

This is my code(input is my word):

string url = "http://de.wikipedia.org/wiki/" + input.Replace(" ", "_");
Process.Start(url);

But when I start the website with Process.Start(url) it starts "http://www.de.wikipedia.org/wiki/XYZ" instead of "http://de.wikipedia.org/wiki/XYZ"

How can I open a website without the www.

Kind regards