Chef and collection of stamps

Chef has a collection of N postage stamps. Each stamp belongs to some type, which are enumerated as positive integers. More valuable stamps have a higher enumerated type. So, type 1 is the least valuable type of stamps, type 2 is a bit more valuable, and so on. Chef often communicates with other philatelists via a stamp exchange website called P-bay. On any particular day, P-bay lists several off