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: Wrong Answer)

#include <stdio.h>

int main() {
	int n, result = 0, memo = 0;
	char str[105];
	int num[200];
	scanf("%d", &n);
	scanf("%s", str);

	for (int i = 0; i < n ; i++) {

		for (int j = 0; j <= i; j++)
		{
			num[str[j]] = 1;
		}

		for (int j = n - 1; j > i; j--)
		{
			if (num[str[j]] == 1)
			{
				memo++;
				num[str[j]] = 0;
			}
		}

		for (int j = 'a'; j <= 'z'; j++)
		{

			num[j] = 0;
		}
		if (memo > result)
		{
			result = memo;
		}
		memo = 0;
	}
	printf("%d", result);
}