NONOPTIONAL

ai al an at in it la li lo na no oi on op pa pi ta ti to

ail ain ait alp alt ani ant apo apt inn ion lap lat lin lip lit loo lop lot nan nap nil nip nit noo not oat oil ono oot opt pal pan pat pia pin pit poi pol poo pot tan tao tap til tin tip ton too top

alit alto anil anon anti atop into iota lain lati linn lino lint lion lipa loan loin loon loop loot lota loti nail naoi nipa noil nolo nona noon nota olio onto opal pail pain pant pial pian pina pint pion pita plan plat plot polo pool poon tail tain tali toil tola tool toon topi topo