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


object Main {
  def read() = {
    val sc = new Scanner(System.in)
    val n = sc.nextInt()
    val str = sc.next()
    (n, str)
  }

  case class PairString(x: String, y: String) {
    def numContainedBoth(): Int = x.distinct.intersect(y.distinct).length
  }

  def main(args: Array[String]): Unit = {
    val (n, str) = read()
    val result =
      (1 until n) //Yの始まるindex
        .map(i => PairString(str.substring(0, i), str.substring(i, n))) // (X,Y)の全体
        .map(pair => pair.numContainedBoth())
        .max

    println(result)
  }
}