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 Rust (1.42.0) (judge verdict: Accepted)

use proconio::input;
use proconio::marker::Chars;
use std::cmp;

fn main() {
    input! {
        s: Chars,
    }
    let mut min = std::usize::MAX;
    let c = 'a';
    for i in 0u8..26 {
        let ch = (c as u8 + i) as char;
        min = cmp::min(min, solve(&s, ch));
    }
    println!("{}", min);
}

fn solve(s: &Vec<char>, ch: char) -> usize {
    if s.iter().all(|c| *c == ch) {
        return 0;
    }
    let mut st = s.clone();
    let mut count = 0;
    let mut flag = true;
    while flag {
        flag = false;
        for i in 0..st.len() - 1 {
            if st[i + 1] == ch {
                st[i] = ch;
            }
            if st[i] != ch {
                flag = true;
            }
        }
        count += 1;
        st.pop();
    }
    return count;
}