You are in charge of all of a certain country's radio broadcasts. At time 0, you send outgoing radio waves to ~N~ (~1 \le N \le 1\,000~) receivers, and whenever a wave meets a receiver, the receiver immediately sends the wave back to you. If the waves travel at the same speed, which incoming radio waves will arrive between time ~S~ and time ~T~ (~1 \le S \le T \le 10\,000~), inclusive?
On one line, ~N~, ~S~ and ~T~, separated by single spaces followed by ~N~ separate lines, each representing the time a radio wave meets a receiver. The times will be positive integers no greater than ~10\,000~.
The number of radio waves that made it back between time ~S~ and time ~T~.
3 2 4 1 2 4
Only the first two radio waves make it back, at times of exactly 2 and 4.