Problem:
Score : 200 points

Problem Statement

You are given a string S of length N consisting of lowercase English letters.
We will cut this string at one position into two strings X and Y.
Here, we would like to maximize the number of different letters contained in both X and Y.
Find the largest possible number of different letters contained in both X and Y when we cut the string at the optimal position.

Constraints

2 \leq N \leq 100

|S| = N

S consists of lowercase English letters.

Input

Input is given from Standard Input in the following format:

N
S

Output

Print the largest possible number of different letters contained in both X and Y.

Sample Input 1

6
aabbca

Sample Output 1

2

If we cut the string between the third and fourth letters into X = aab and Y = bca, the letters contained in both X and Y are a and b.
There will never be three or more different letters contained in both X and Y, so the answer is 2.

Sample Input 2

10
aaaaaaaaaa

Sample Output 2

1

However we divide S, only a will be contained in both X and Y.

Sample Input 3

45
tgxgdqkyjzhyputjjtllptdfxocrylqfqjynmfbfucbir

Sample Output 3

9

Solution in Rust (1.15.1) (judge verdict: Accepted)

fn read<T: std::str::FromStr>() -> T {
    let mut s = String::new();
    std::io::stdin().read_line(&mut s).ok();
    s.trim().parse().ok().unwrap()
}

fn read_vec<T: std::str::FromStr>() -> Vec<T> {
    read::<String>()
        .split_whitespace()
        .map(|e| e.parse().ok().unwrap())
        .collect()
}

fn read_vec2<T: std::str::FromStr>(n: u32) -> Vec<Vec<T>> {
    (0..n).map(|_| read_vec()).collect()
}
fn main(){
    let n  = read::<i32>();
    let s = read::<String>();
    let cs = s.chars().collect::<Vec<char>>();
    let mut ans = Vec::new();
    for i in 1..n{
        let mut sub = cs.clone();
        let mut cut = sub.split_at(i as usize);
        let mut a1 = cut.0.to_vec();
        let mut a2= cut.1.to_vec();
        a1.sort();
        a2.sort();
        a1.dedup();
         a2.dedup();
        // let a1:Vec<char> = cut.0.to_vec().dedup().collect();
        // let a2:Vec<char> = cut.1.to_vec().dedup().collect();
        let count = a1.iter().fold(0,|x,y| {match  a2.contains(y) {
                true => x + 1,
                false => x,
        }});

        ans.push(count);    
    }
    // ans.sort_by_key(|&(a,b)|b);
    println!("{}",ans.iter().max().unwrap());
}