A boot shop has received a shipment from the factory consisting of N left boots and N right boots. Each boot has some integer size, and a left and right boot will form a proper pair if they have equal sizes. Each boot can only belong to a single pair. The employees of the boot store want to create N proper pairs of boots. Fortunately, the factory has offered to exchange any number of boots in the shipment with new boots of different sizes.
You are given a int left and a int right containing the sizes of the left boots and right boots, respectively.
Return the least number of boots that must be exchanged.