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)

input = STDIN.gets.chomp.split("")

len = input.count
cnt = Hash.new(0)

input.each { |e| cnt[e]+=1 }

# p len
ans = (len/2).to_i

if cnt.values().all? { |e| e==1 }
else
  cnt.each{|key,val|
    if val>1
      # p key
      pos_list = []
      input.each_with_index { |e, i|  
        pos_list.push i if e == key
      }
      # p pos_list
      cand_list = [pos_list.first,len-pos_list.last-1]
      (pos_list.length()-1).times { |n|
        cand_list.push( ((pos_list[n+1]-pos_list[n]-1)/1).to_i )
      }
      # p cand_list
      _ans = cand_list.max
      ans = _ans if _ans < ans
    end
  }
end

print ans