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 scala.io.StdIn

object Main extends App {
  val n = StdIn.readLine().toInt
  val s = StdIn.readLine()

  val all = s.distinct.sorted
  val r = (1 until n).foldLeft(0) { (ac, index) =>
    val r = s.splitAt(index)
    //println(r)
    scala.math.max(ac, all.foldLeft(0){ (acc, c) =>
      acc + (if(r._1.contains(c) && r._2.contains(c)) 1 else 0)
    })
  }
  
  println(r)
}