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# (Mono 4.6.2.0) (judge verdict: Accepted)

// A Dynamic Programming based 
// C# program to find minimum 
// number operations to 
// convert str1 to str2 
using System;
using System.Collections.Generic;
using System.Linq;
class GFG
{

    public static void Main()
    {
        var n = int.Parse(Console.ReadLine());
        var t = Console.ReadLine();
        CutCount(t, n);
    }

    static void CutCount(string s, int n)
    {

        var ss = s;
        int max = 0;
        for (int i = 1; i < ss.Count(); i++)
        {
            var sub1 = ss.Substring(0, i);
            var sub2 = ss.Substring(i);
            var c1 = sub1.Intersect(sub2).Count();
            max = Math.Max(max,c1);

        }
        Console.Write(max);

    }



}