20457
After a long design and experimentation period beginning in 1873 , HMS Inflexible with 4 guns became the only ship to mount them , in 1880 .
 None
Given options, please tell me the categories of all the listed entity words.Output format is "type1: word1; type2: word2". 
Option: location, person, organization 
Text: {0} 
 Entities:  
Answer:
 None