public interface Dictionary<K,V>
{
    public int size();         // Return # entries in the dictionary

    public void put(K k, V v); // Insert (k,v) if k not in dictionary
                               // Otherwise update v for key k

    public V get(K k);         // Returns the value v for key k
                               // Return null if k not in dictionary

    public V remove(K k);      // Remove entry (k, v) from dictionary
                               // Return v when k found
		 	       // Otherwise return null
}