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++14 (GCC 5.4.1) (judge verdict: Wrong Answer)

#include <cstdio>
#include <iostream>
#include <string>
#include <map>
using namespace std;

int main(){
    int index;
    scanf("%d", &index);
   
    char *str = (char *)malloc(sizeof(char) * index);
    scanf("%s", str);

    map<char, int> mp;

    int *max_ar = (int *)malloc(sizeof(int) * index);
    int num;
    int max = 0;
    int max_index = 1;
    int i, j, k;
    for(i=0; i<(index-1); i++){
        mp[str[i]] = 0;
        for(auto itr = mp.begin(); itr != mp.end(); ++itr){
            itr->second = 0;
        }

        for(j=i; j<index; j++){
            if(mp.find(str[j]) != mp.end()){
                mp[str[j]] = 1;
                //cout << str[j];
            }
        }

        num = 0;
        for(auto itr = mp.begin(); itr != mp.end(); ++itr){
            num += itr->second;
        }

        if(max < num){
            max = num;
        }
    }
    printf("%d\n", max);
    return 0;
}