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 Ruby (2.3.3) (judge verdict: Accepted)

require 'pp'

# 入力値を文字列で返却する
def gets_s()
  gets.chomp
end
str = gets_s
s_list = str.chars
s_count_hash = s_list.group_by(&:itself).map{|k,v| [k, v.count] }.to_h

chars = ("a".."z").to_a
counts = chars.map do |char|
  count = 0
  duped_s_list = s_list.dup
  while duped_s_list.uniq.size != 1 do
    duped_s_list.pop
    duped_s_list.size.times do |i|
      duped_s_list[i] = char if duped_s_list[i+1] == char
    end
    count += 1
  end
  count
end
puts counts.min