ROUNDTRIPPING

do go id in it no nu od oi on op or pi ti to un up ut

dig din dip dit dog don dor dot dug dui dun duo dup gid gin gip git gnu god gor got gun gut inn ion nip nit nod nog nor not nun nut opt ort oud our out pig pin pip pit piu pod poi pop pot pro pud pug pun pup pur put rid rig rin rip rod rot rug run rut tin tip tod tog ton top tor tug tui tun tup udo upo urd urn urp

ding dino dint dipt dirt doit dong dorp dorr dour drip drop drug duit dung dunt durn duro durr gird girn giro girt gorp gout grid grin grip grit grot guid inro inti into irid iron nidi nodi noir nori noun nurd ping pint pion pirn pond pong porn port pour pout prig prod prog prop ptui pung punt puri purr rind ring riot roti roup rout ruin rung runt ting tipi tiro tong topi tori torn torr tour trig trio trip trod trog trop trug tung turd turn udon undo unit unto updo upon