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-1;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);
}