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 (Clang 3.8.0) (judge verdict: Wrong Answer)

#include<stdio.h>
#include<string.h>
int main(){
  int n,max = 0;
  scanf("%d",&n);
  char s[200],c[2][n][200];
  scanf("%s",&s);
  for(int i = 1;i < n;i++){
    for(int j = 0;j < i;j++){
      c[0][i][j] = s[j];
    }
    for(int j = i;j < n;j++){
      c[1][i][j] = s[j - i];
    }
    int cnt = 0;
    for(int k = 0;k < 26;k++){
      char a[2] = {'a' + k};
      if(strstr(c[0][i],a) != NULL && strstr(c[1][i],a) != NULL){
        cnt++;
      }
    }
    if(max < cnt){
      max = cnt;
    }
  }
  printf("%d\n",max);
  return 0;
}