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: Wrong Answer)

import java.util.Scanner;

public class Main{

	public static void main(String[] args) {
		int[] mojicountR = new int[26];
		int[] mojicountL = new int[26];
		int len;
		int tmax = 0,max = 0;
		String str = new String();
		Scanner scan = new Scanner(System.in);

		for(int i = 0;i < 26;i++) {
			mojicountR[i] = 0;
			mojicountL[i] = 0;
		}

		len = scan.nextInt();
		str = scan.next();

		for(int i = 0;i < len;i++) {
			mojicountR[str.charAt(i) - 97]++;
		}

		for(int i = 0;i < len;i++) {
			tmax = max;
			if(--mojicountR[str.charAt(i) - 97] == 0) {
				tmax--;
			}
			if(++mojicountL[str.charAt(i)- 97] == 1) {
				tmax++;
			}

			max = getmax(max,tmax);
		}

		System.out.println(max);

		scan.close();

	}

	public static int getmax(int x,int y) {
		return x > y ? x :y ;
	}

	public static int getmin(int x,int y) {
		return x > y ? y : x;
	}

}