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 Kotlin (1.0.0) (judge verdict: Accepted)

import java.io.InputStream
import java.math.BigDecimal
import java.math.BigInteger

private val MOD = 1e9.toLong() + 7

val input = FastScanner()

fun main(args: Array<String>) = input.run {
    val s = nextString()!!.toCharArray()
    val ans = ('a'..'z').map { c ->
        generateSequence(s.map { it == c }.toBooleanArray()) {
            t -> BooleanArray(t.size - 1) { t[it] || t[it + 1] }
        }.indexOfFirst { it.all { it } }
    }.min()
    println(ans)
}

fun String.toBigInteger() = BigInteger(this)
fun String.toBigDecimal() = BigDecimal(this)

class FastScanner(private val input: InputStream = System.`in`) {
    private val sb = StringBuilder()
    private val buffer = ByteArray(4096)
    private var pos = 0
    private var size = 0

    fun nextString(): String? {
        var c = skipWhitespace()
        if (c < 0) return null

        return sb.run {
            setLength(0)

            do {
                append(c.toChar())
                c = read()
            } while (c > ' '.toInt())

            toString()
        }
    }

    fun nextLine(): String? {
        var c = read()
        if (c < 0) return null

        return sb.run {
            setLength(0)

            while (c >= 0 && c != '\n'.toInt()) {
                append(c.toChar())
                c = read()
            }

            toString()
        }
    }

    fun nextLong(): Long {
        var c = skipWhitespace()

        val sign = if (c == '-'.toInt()) {
            c = read()
            -1
        } else 1

        var ans = 0L

        while (c > ' '.toInt()) {
            ans = ans * 10 + c - '0'.toInt()
            c = read()
        }

        return sign * ans
    }

    fun nextInt() = nextLong().toInt()
    fun nextDouble() = nextString()?.toDouble() ?: 0.0
    fun nextBigInteger(): BigInteger = nextString()?.toBigInteger() ?: BigInteger.ZERO
    fun nextBigDecimal(): BigDecimal = nextString()?.toBigDecimal() ?: BigDecimal.ZERO

    fun nextStrings(n: Int) = Array<String>(n) { nextString() ?: "" }
    fun nextInts(n: Int) = IntArray(n) { nextInt() }
    fun nextLongs(n: Int) = LongArray(n) { nextLong() }
    fun nextDoubles(n: Int) = DoubleArray(n) { nextDouble() }
    fun nextBigIntegers(n: Int) = Array<BigInteger>(n) { nextBigInteger() }
    fun nextBigDecimals(n: Int) = Array<BigDecimal>(n) { nextBigDecimal() }

    fun nextStrings(n: Int, m: Int) = Array(n) { nextStrings(m) }
    fun nextInts(n: Int, m: Int) = Array(n) { nextInts(m) }
    fun nextLongs(n: Int, m: Int) = Array(n) { nextLongs(m) }
    fun nextDoubles(n: Int, m: Int) = Array(n) { nextDoubles(m) }
    fun nextBigIntegers(n: Int, m: Int) = Array(n) { nextBigIntegers(m) }
    fun nextBigDecimals(n: Int, m: Int) = Array(n) { nextBigDecimals(m) }

    private fun skipWhitespace(): Int {
        while (true) {
            val c = read()
            if (c > ' '.toInt() || c < 0) return c
        }
    }

    private fun read(): Int {
        while (pos >= size) {
            if (size < 0) return -1
            size = input.read(buffer, 0, buffer.size)
            pos = 0
        }
        return buffer[pos++].toInt()
    }
}