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: Wrong Answer)

#include <stdio.h>
#include<string.h>

int main(){
  int len;
  char s[100];
  int c;
  scanf("%d", &len);
  int p;
  char ls[100];
  char rs[100];
  char matchs[100];
  char ts[2];
  
  p = 1;
  int lp, rp;
  int i,j;
  
  
  int maxc = 0;
  lp = 1; // ひだりの長さ
  while(lp < len){
  	c = 0;
    
    for(i = 0; i < 100; i++)
    matchs[i] = '\0';
    
    strcpy(rs, &s[lp]);
    
    for(j = 0; j < lp; j++){
      ts[0] = s[j];
      ts[1] = '\0';
    	if((strstr(rs,ts) != NULL) && (strstr(matchs, ts) == NULL)){ // 左の文字列があるとき
    
      	strcat(matchs, ts);
      	c++;
    
   		}
    
    }
    if(maxc < c)
        maxc = c;
  lp++;
}
 
    printf("%d\n", c);
  return 0;
}