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)

s = gets.chomp.split("")

n = s.length

if s.uniq.length == 1 then
  puts 0
elsif s.uniq.length == n then
  puts n / 2
else
  h = Hash.new(0)
  s.each do |c|
    h[c] += 1
  end
  ret = n
  h.each do |k, v|
    if v > 1 then
      ind = [0]
      cand = []
      s.each_with_index do |c, i|
        if c == k
          ind << i 
          cand << i - ind[-2] - 1
        end
      end
      cand[0] += 1
      cand << n-1 - ind[-1]
      ret = [ret, cand.max].min
    end
  end
  puts ret
end