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 Pascal (FPC 2.6.2) (judge verdict: Accepted)

program Project1;

{$APPTYPE CONSOLE}

uses
  SysUtils;
var
  a,h,w,i,j,count,x,y,sw,m,n,b,c,soeji,sum,max,k:Integer;
  l:array of Integer;
  s,s123,s1,s2,s3:string;
  al:string = 'abcdefghijklmnopqrstuvwxyz';
  tf,tfl,tfr:Boolean;
begin
  try
    { TODO -oUser -cConsole メイン : ここにコードを記述してください }
    Readln(n);
    Readln(s);
    count:=0;
    max  :=0;

    for i:=1 to n do begin //区切り位置変更

      for k:=1 to 26 do begin
        tfl:=false;
        tfr:=false;
        for j:=1 to i do begin //左
            if al[k]=s[j]then
              tfl:=true;
        end;
        for j:=i+1 to n do begin //右
            if al[k]=s[j]then
              tfr:=true;
        end;
        if tfl and tfr then
          inc(count);
      end;

      max:=(count+max+abs(count-max))div 2;
      count:=0;
    end;

    Writeln(max);
    Readln;
  except
    on E: Exception do
      Writeln(E.ClassName, ': ', E.Message);
  end;
end.