Problem:
Score : 200 points

Problem Statement

A string is called a KEYENCE string when it can be changed to keyence by removing its contiguous substring (possibly empty) only once.

Given a string S consisting of lowercase English letters, determine if S is a KEYENCE string.

Constraints

The length of S is between 7 and 100 (inclusive).

S consists of lowercase English letters.

Input

Input is given from Standard Input in the following format:

S

Output

If S is a KEYENCE string, print YES; otherwise, print NO.

Sample Input 1

keyofscience

Sample Output 1

YES

keyence is an abbreviation of key of science.

Sample Input 2

mpyszsbznf

Sample Output 2

NO

Sample Input 3

ashlfyha

Sample Output 3

NO

Sample Input 4

keyence

Sample Output 4

YES

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

let s = read_line ()

let k = "keyence"

let s_len = String.length s

let rec loop si ki r =
  if si = s_len then
  print_string @@ if ki = 7 then "YES" else "NO"
  else if ki = 7 then
    print_string @@ if si = s_len then "YES" else "NO"
  else
    if s.[si] = k.[ki] then
      loop (si + 1) (ki + 1) r
    else if r = 0 then print_string "NO"
    else
      let rec f i = if i = s_len then -1 else if s.[i] = k.[ki] then i else f (i + 1) in
      let ni = f si in
      if ni = -1 then print_string "NO"
      else loop (ni + 1) (ki + 1) 0

let () = loop 0 0 1