Fleet Dock Assignment Ledger

A shipping fleet's dispatch office keeps a ledger mapping numeric dock identifiers to the identifier of whichever vessel currently occupies that dock. Over the course of a shift, three kinds of instructions arrive: SET dock vessel records that vessel now occupies dock (overwriting whatever vessel, if any, was previously recorded there); GET dock asks which vessel currently occupies dock, reported as -1 if the dock is currently unoccupied; and REMOVE dock frees dock, so it becomes unoccupied (doing nothing if it was already unoccupied). Process every instruction in order and, for each GET, report its answer.

Input format

• Line 1: an integer q, the number of instructions.
• Each of the next q lines is one instruction: SET dock vessel, GET dock, or REMOVE dock.

Output format

For every GET instruction, print its answer on its own line, in the order the GET instructions appear. Print nothing for SET or REMOVE.

Constraints

• 1 <= q <= 10^4
• 0 <= dock <= 10^6
• 0 <= vessel <= 10^6

6
SET 1 10
SET 2 20
GET 1
REMOVE 1
GET 1
GET 2

10
-1
20

5
GET 5
SET 5 100
SET 5 200
GET 5
REMOVE 10

-1
200