Problem:
Search III

Your task is to write a program of a simple dictionary which implements the following instructions:

insert str: insert a string str in to the dictionary

find str: if the distionary contains str, then print 'yes', otherwise print 'no'

Input

In the first line n, the number of instructions is given. In the following n lines, n instructions are given in the above mentioned format.

Output

Print yes or no for each find instruction in a line.

Constraints

A string consists of 'A', 'C', 'G', or 'T'

1 ≤ length of a string ≤ 12

n ≤ 1000000

Sample Input 1

5
insert A
insert T
insert C
find G
find A

Sample Output 1

no
yes

Sample Input 2

13
insert AAA
insert AAC
insert AGA
insert AGG
insert TTT
find AAA
find CCC
find CCC
insert CCC
find CCC
insert T
find TTT
find T

Sample Output 2

yes
no
no
yes
yes
yes

Notes

Template in C

Solution in OCaml (judge verdict: Accepted)

module SS = Set.Make(String);;

let _ =
  let n = read_int () and
      s = SS.empty
  in
  let rec read s = function
      0 -> ()
    | i ->
       let line = read_line () |> Str.split (Str.regexp " ") |> Array.of_list in
       if line.(0) = "insert" then
         read (SS.add line.(1) s) (i-1)
       else if line.(0) = "find" then
         begin
           if SS.mem line.(1) s then print_endline "yes"
           else print_endline "no"
          ;read s (i-1)
         end
  in read s n;;