843
The  Empire of Japan  received six U-boats as a reparation payment after World War I. The  IJN  copied and designed the I-21 class ( later renamed I-121 class ) minelaying submarine .
 country of headquarters: Empire of Japan, IJN
Given a phrase that describes the relationship between two words, extract the words and the lexical relationship between them. The output format should be "relation1: word1, word2; relation2: word3, word4". 
Option: cities of residence, top members employees, members, alternate names, origin, state or provinces of residence, title of person, spouse, city of headquarters, NA, founded by, state or province of headquarters, employee of, countries of residence, country of birth, founded, subsidiaries, country of headquarters 
Text: {0} 
Answer:
 country of headquarters: Empire of Japan, IJN