Problem:
Score : 300 points

Problem Statement

Snuke can change a string t of length N into a string t' of length N - 1 under the following rule:

For each i (1 ≤ i ≤ N - 1), the i-th character of t' must be either the i-th or (i + 1)-th character of t.

There is a string s consisting of lowercase English letters.
Snuke's objective is to apply the above operation to s repeatedly so that all the characters in s are the same.
Find the minimum necessary number of operations.

Constraints

1 ≤ |s| ≤ 100

s consists of lowercase English letters.

Input

Input is given from Standard Input in the following format:

s

Output

Print the minimum necessary number of operations to achieve the objective.

Sample Input 1

serval

Sample Output 1

3

One solution is: serval → srvvl → svvv → vvv.

Sample Input 2

jackal

Sample Output 2

2

One solution is: jackal → aacaa → aaaa.

Sample Input 3

zzz

Sample Output 3

0

All the characters in s are the same from the beginning.

Sample Input 4

whbrjpjyhsrywlqjxdbrbaomnw

Sample Output 4

8

In 8 operations, he can change s to rrrrrrrrrrrrrrrrrr.

Solution in Haskell (GHC 7.10.3) (judge verdict: Accepted)

import Data.Char (chr,ord)
import Data.Maybe (fromJust,isJust)

trans [] _ = []
trans [_] _ = []
trans (x:y:s) c
  | y == c = y:trans (y:s) c
  | otherwise = x:trans (y:s) c

solve :: String -> Int -> Char -> Int
solve s n c =
  if s == replicate (length s) c
    then n
    else
      solve ns (n+1) c
  where ns = trans s c

main = do
  s <- getLine :: IO String
  print $ minimum $ map (solve s 0.chr) [ord 'a'..ord 'z']