补票

补票	bǔ piào	to buy or upgrade a ticket after boarding a train, boat etc / to buy a ticket for a show after having sat down in the theater
补	bǔ	to repair / to patch / to mend / to make up for / to fill (a vacancy) / to supplement
票	piào	ticket / ballot / banknote / CL:张 / person held for ransom / amateur performance of Chinese opera / classifier for groups, batches, business transactions