Task: Text Categorization
Input (English): Text:  The Type 61 Salisbury class were a class of four British aircraft direction (AD) (or radar picket) frigates built for the Royal Navy.These ships were related to the Type 41 Leopard class frigates but with reduced armament (one twin 4.5 inch mount vice two) to make way for more aircraft direction equipment particularly the four-ton radar antenna of the Type 965 (AKE-2).
Output (English): 6