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 a[30] ={};
  int b[30] ={};
  string s,s2,s3;
  int n,mn =0;

  cin >> n >> s;


  for(int i=0;i<s.size();i++)
    {
      int cnt =0,cnt2 =0;
      s2 =s.substr(0,i);
      s3 = s.substr(i);
      for(int j=0;j<s2.size();j++)
	{
	  a[s2[j ]-'a']++;
	}
      for(int k=0;k<s3.size();k++)
	{
	  b[s3[k]-'a']++;
	}

      for(int l =0;l<30;l++)
	{
	  if(a[l] > 0)
	    {
	      cnt++;
	      a[l] = 0;
	    }
	  if(b[l] >0)
	    {
	      cnt2++;
	      b[l] = 0;
	    }
	}
      if(mn <= min(cnt,cnt2))
	{
	  mn = min(cnt,cnt2);
	}
      cnt =0,cnt2=0;
    }
  cout << mn << endl;

  return 0;
}