Problem:
Score : 100 points

Problem Statement

A Hitachi string is a concatenation of one or more copies of the string hi.

For example, hi and hihi are Hitachi strings, while ha and hii are not.

Given a string S, determine whether S is a Hitachi string.

Constraints

The length of S is between 1 and 10 (inclusive).

S is a string consisting of lowercase English letters.

Input

Input is given from Standard Input in the following format:

S

Output

If S is a Hitachi string, print Yes; otherwise, print No.

Sample Input 1

hihi

Sample Output 1

Yes

hihi is the concatenation of two copies of hi, so it is a Hitachi string.

Sample Input 2

hi

Sample Output 2

Yes

Sample Input 3

ha

Sample Output 3

No

Solution in OCaml (4.02.3) (judge verdict: Wrong Answer)

let s = read_line()

let rec f i b =
  try
    let c = s.[i] in
    if b then
      begin
        if c <> 'h' then "No"
        else f (i+1) false
      end
    else
      if c = 'i' then f (i+1) true
      else "No"
  with Invalid_argument _ -> "Yes"

let () = print_endline (f 0 true)