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 Scala (2.11.7) (judge verdict: Accepted)

import java.util.Scanner;
import scala.collection.immutable.Set;

object Main{
  def main(args: Array[String]){
    val sc = new Scanner(System.in);
    val n = sc.nextInt;
    sc.nextLine;
    val s: String = sc.nextLine;

    println((for(i <- 1 to s.length-1) yield {
      s.splitAt(i) match{
        case (f,s) => {
          (f.toCharArray.toSet & s.toCharArray.toSet).size;
        }
      }
    }).max);
  }
}