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: Runtime Error)

module SS = Set.Make(String)

let _ =
  let n = read_int () in
  let s = SS.empty in
  let rec read i acc =
    if i >= n then acc
    else begin
      match Str.split (Str.regexp_string " ") (read_line ()) with
      | [] | [_] -> exit 1
      | op :: x :: _ -> read (i + 1) ((op, x) :: acc)
    end
  in
  let cmds = read 0 [] in
  let doit (op, x) s =
    if op = "insert" then SS.add x s
    else if op = "find" then (print_endline (if SS.mem x s then "yes" else "no"); s)
    else exit 1
  in
  List.fold_right doit cmds s