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(void)
{
	int N;

	scanf("%d", &N);
	char str[1001];
	scanf("%s", str);

	int i;
	int s;
	int ans;
	ans = 0;
	for (i = 0;i <= N; i++)
	{
		s = 0;
		int p;
		int q;
		p = 0;
		q = i+1;
		int y;
		y = 1;

		do {
			do {
				if (str[p] = str[q])


				{
					int k;
					int w = 0;
					k = 0;
					do{
						if (str[p] = str[k])
							w = w;
						else
							w++;
						k++;
					} while (k <= p);
					if (w >= 1)
						s++;
					else
						s = s;
				}
				else
					s = s;
				q++;
			}while (q <= N);
			p++;
		}while (p <= i);
		if (s >=ans)
			ans = s;
		else
			ans = ans;
		s = 0;
		

	}

	printf("%d", ans);
	return 0;
	





}