using System;

public class Program

{

    public static void Main()

    {

        string result = "123456  as   we     test";

        var result2 = result.Substring(0, 6) + String.Join(" ", result.Substring(6, result.Length - 6).Split(new char[] { ' ' }, StringSplitOptions.RemoveEmptyEntries));

        Console.WriteLine(result2);

    }

}