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 (2.7.1) (judge verdict: Accepted)

s = gets.chomp
array = s.split("").map {|c| 2**(c.ord - 97) }

ret = 0
while array.length > 1 do
    r = array[0]
    (1..(array.length-1)).each do |i|
        r = r & array[i]
        break if r == 0
    end
    if r != 0
        break
    else
        ret+=1
        next_array = []
        (0..(array.length-2)).each do |i|
            next_array.push(array[i] | array[i+1])
        end
        array = next_array
    end
end
puts ret