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 <bits/stdc++.h>
using namespace std;

int main()
{
    int x;
    cin>>x;
    string a,b,c;

    cin>>a;

    int counter=0;
if(a.size()%2!=0){
 b=a.substr(0,a.size()/2+1); 
c=a.substr(a.size()/2+1,a.size()); 
}
else{
  b=a.substr(0,a.size()/2); 
 c=a.substr(a.size()/2,a.size());   
}
set<char>s1;
set<char>s2;
for(int i=0;i<b.size();i++)
{
    s1.insert(b[i]);
    s2.insert(c[i]);
}
for(int i=0;i<b.size();i++)
{
    for(int j=0;j<a.size();j++)
    {
        if(b[i]==c[j])counter++;
    }
}
cout<<counter;

return 0;

}