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 5.4.1) (judge verdict: Accepted)

#include <stdio.h>
#include <math.h>
#include <stdbool.h>
int main(void){
  int n;
  char s[101];
  scanf("%d %s",&n,s);
  int i,j,max=0;
  for(i=1;i<n;i++){
    int count=0;
    for(char c='a';c<='z';c++){
      bool l=false,r=false;
      for(j=0;j<i;j++){
        if(s[j]==c) l=true;
      }
      for(j=i;j<n;j++){
        if(s[j]==c) r=true;
      }
      if(l&&r) count++;
    }
     if(max<count) max=count;
  }
  printf("%d",max);
  return 0;
}