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 Java8 (OpenJDK 1.8.0) (judge verdict: Accepted)

import java.util.*;
public class Main{
	public static void main(String[] args){
    	Scanner sc = new Scanner(System.in);
      int n = sc.nextInt();
      char[] s = sc.next().toCharArray();
      int count = 0;
      int max = 0;
      boolean left = false;
      boolean right = false;
      for(int i = 0;i < n;i++){
        count = 0;
        left = false;
        right = false;
      	for(char x = 'a';x <= 'z';x++){
          left = false;
          right = false;
      		for(int j = 0;j < i;j++){
            	if(s[j]==x) left = true;
            }
            for(int j = i;j < n;j++){
            	if(s[j]==x) right = true;
            }
          if(left&&right)count++;
      	}
        max = Math.max(max,count);
      }
      System.out.println(max);
    }
}