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, marker::Chars};
use std::collections::HashSet;

fn main() {
    input! {
        s: Chars,
    }

    let mut chars = HashSet::new();

    for &c in s.iter() {
        chars.insert(c);
    }

    let mut min = None;

    for c in chars {
        let mut s = s.clone();
        let mut count = 0;
        while s.iter().any(|&e| e != c) {
            for i in 0..s.len()-1 {
                if s[i] == c || s[i+1] == c {
                    s[i] = c;
                }
            }
            s.pop();
            count += 1;
        }
        if let Some(min) = min.as_mut() {
            *min = std::cmp::min(count, *min);
        } else {
            min = Some(count);
        }
    }

    if let Some(min) = min {
        println!("{}", min);
    } else {
        unreachable!();
    }
}