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 C# (Mono 4.6.2.0) (judge verdict: Wrong Answer)

using System;
using System.Linq;
using System.Collections.Generic;

public class Program
{
    public static void Main()
    {
        var s = Console.ReadLine();

        var modes = Enumerable.Range('a', 'z' - 'a' + 1)
            .GroupJoin(s, x => x, x => x, (x, xs) => new { x, k = xs.Count() } )
            .GroupBy(x => x.k, x => x.x)
            .OrderByDescending(x => x.Key)
            .First();
        if (modes.Count() == s.Length)
        {
            Console.WriteLine(s.Length / 2);
            return;
        }

        var minimum = int.MaxValue;
        foreach (var mode in modes)
        {
            var t = s + mode;
            var modeIndices = t
                .Select((x, i) => new { x, i })
                .Where(x => x.x == mode)
                .Select(x => x.i)
                .ToArray();
            var interval = modeIndices.Skip(1)
                .Zip(modeIndices, (x, y) => x - y)
                .Concat(new [] { 0 })
                .Max();
            minimum = Math.Min(minimum, interval);
        }
        Console.WriteLine(minimum - 1);
    }
}