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 C (GCC 5.4.1) (judge verdict: Accepted)

#include <stdio.h>

int main()
{
	int NUM[100];
	int BOOLEANS[100];
	for(int i = 0; i < 100; i++)
	{
		NUM[i] = 0;
		BOOLEANS[i] = 0;
	}
	int N = 0;
	scanf("%d", &N);
	char S[100];
	scanf("%s", S);
	
	for(int i = 0; i < N; i++)
	{
		if(BOOLEANS[i] == 0)
		{
			BOOLEANS[i] = 1;
			int tem = 0;
			for(int j = i + 1; j < N; j++)
			{
				if(S[i] == S[j])
				{
					//printf("%c %d\n", S[j], j);
					BOOLEANS[j] = 1;
					tem = j;
				}
			}
			for(int j = i; j < tem; j++)
			{
				//printf("%d ", j);
				NUM[j]++;
			}
		}
	}
	int max = 0;
	for(int i = 0; i < N; i++)
	{
		if(max < NUM[i]) max = NUM[i];
	}
	printf("%d\n", max);
	return 0;
}