namespace Invercargill {
    namespace DataStructures {
        public class HashSet {
            public void add (string item) {}
            public void remove (string item) {}
            public bool contains (string item) { return false; }
        }
        
        public class LinkedList {
            public void append (string item) {}
            public void prepend (string item) {}
        }
    }
    
    namespace Utils {
        public class StringHelper {
            public static string to_upper (string input) { return input; }
        }
    }
}