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 JavaScript (node.js v5.12) (judge verdict: Accepted)

'use strict'

function Main(input) {
  const N = Number(input.split('\n')[0]);
  const S = input.split('\n')[1].split('');

  let S_left, S_right;
  let counter = 0;
  let sufferlist = [];


  for(let i=1; i<N; i++) {
    S_left = S.slice(0, i)
      .filter((x,i,self) => self.indexOf(x) === i);
    S_right = S.slice(i)
      .filter((x,i,self) => self.indexOf(x) === i);

    for(let j=0; j<S_left.length ;j++) {
      if(S_right.some(value => value === S_left[j])) {
        counter++;
      }
    }
    sufferlist.push(counter);
    counter = 0;
    
    //console.log(S_left);
    //console.log(S_right);
    //console.log(sufferlist);
  }

  console.log(Math.max.apply(null, sufferlist));

}

Main(require("fs").readFileSync("/dev/stdin", "utf8").trim());