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)

#[allow(dead_code)]

pub struct Scanner {
    idx: usize, 
    buf: Vec<String>,
}

impl Scanner {
    pub fn new<T: std::io::Read>(inf: &mut T) -> Scanner {
        Self {
            idx:0,
            buf: {
                let mut s = String::new();
                inf.read_to_string(&mut s).expect("I/O error");
                s.split_whitespace().map(|x| x.to_owned()).collect()
            },
        }
    }

    pub fn read<T: std::str::FromStr> (&mut self) -> T 
    where
        <T as std::str::FromStr>::Err: std::fmt::Debug,
    {
        if self.empty() {
            panic!("reached the end of input")
        }
        let ret = self.buf[self.idx].parse::<T>().expect("parse error");
        self.idx += 1;
        return ret;
    }

    pub fn empty(&self) -> bool {
        return self.idx >= self.buf.len();
    }
}

fn main() {
    let mut sc = Scanner::new(&mut std::io::stdin());
    let s: Vec<char> = sc.read::<String>().chars().collect();

    let mut ans = 1 << 30;

    let is_unique = |s: &Vec<char>| {
        for i in 1..s.len() {
            if s[i] != s[i - 1] {
                return false;
            }
        }
        return true;
    };

    let x = 'a' as u8;
    let y = 'z' as u8;
    for ch in x..=y {
        let mut cpy = s.clone();
        let mut cnt = 0;

        while !is_unique(&cpy) {
            cnt += 1;
            for i in 1..cpy.len() {
                if cpy[i] == ch as char {
                    cpy[i - 1] = cpy[i];
                }
            }
            cpy.pop();
        }

        ans = std::cmp::min(ans, cnt);
    }

    println!("{}", ans);
}