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 9.2.1) (judge verdict: Runtime Error)

#include<bits/stdc++.h>
#define ll long long
using namespace std;
int main()
{
	ios_base::sync_with_stdio(false),cin.tie(NULL);
	int n,c=0;
	cin>>n;
	string s;
	cin>>s;
	string s1,s2;
	vector<int>v;
	for(int i=1;i<n-1;i++)
	{
		s1=s.substr(0,i);
		s2=s.substr(i,n-1);
		int a[26],b[26];
		memset(a,0,sizeof(a));
	    memset(b,0,sizeof(b));
		for(int i=0;i<s1.size();i++)
	{
		int x=s1[i]-'a';
		a[x]++;
	}
	for(int i=0;i<s2.size();i++)
	{
		int y=s2[i]-'a';
		b[y]++;
	}
	for(int i=0;i<26;i++)
	{
		if(a[i]>0 && b[i]>0)
		{
			c++;
		}
	}
	v.push_back(c);
	c=0;
	}
	sort(v.rbegin(),v.rend());
	cout<<v[0]<<endl;
	return 0;
}