N or M?

["Fiction" "Married people" "Mystery" "Private investigators" "Tommy Beresford (Fictitious character)" "Tuppence Beresford (Fictitious character)" "Spy stories" "Large type books" "Fiction mystery & detective traditional" "London (england) fiction" "England fiction" "World war 1939-1945 fiction" "Beresford tommy (fictitious character) fiction" "Beresford tuppence (fictitious character) fiction" "Fiction thrillers espionage" "Fiction mystery & detective women sleuths" "Fiction family life general" "Fiction mystery & detective general" "Private investigators fiction" "Married people fiction" "D\u00e9tectives" "Romans nouvelles" "Couples mari\u00e9s"]