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<iostream>
#include<algorithm>
#include<string>

using namespace std;

int main(void){
    int N;
    int ans,cut;
    cut=ans=0;
    string S;
    

    cin>>N>>S;
    
    for(int i=1;i<N;i++){
        
        for(char c='a';c<='z';c++){
            bool right=false; bool left= false;
            
            for(int j=0;j<i;j++){
                if(S[j]==c){
                    left=true;
                }
            }
    
            for(int j=i;j<N;j++){
                if(S[j]==c){
                    right=true;
                }
            }

            if(right==true&&left==true){
                cut++;
            }

        }

        if(ans<cut){
            ans==cut;
        }
        cut=0;

    }


    cout<<ans<<endl;
    return 0;
}