bi1 bu3 bi1 bu3
bi1 bu3 bi1 bu3
on on on on
bi1 bu3 bi1 bu3 .
p i˥ WORD_BOUNDARY p u˧ WORD_BOUNDARY p i˥ WORD_BOUNDARY p u˧ WORD_BOUNDARY
b i 1 WORD_BOUNDARY b u 3 WORD_BOUNDARY b i 1 WORD_BOUNDARY b u 3 WORD_BOUNDARY . WORD_BOUNDARY