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>
int main(void){
    int n,i,j,ans=0;
    char s[101];
    scanf("%d",&n);
    scanf("%s",s);
    for(i=0;i<n;i++){
        int cnt=0;
        int x[26]={0};
        int y[26]={0};
        for(j=0;j<n;j++){
            if(i>j) x[s[j]-'a']=1;
            else y[s[j]-'a']=1;
        }
        for(j=0;j<26;j++){
            if(x[j]==1 && x[j]==y[j]) cnt++;
        }
        if(cnt>ans) ans=cnt;
    }
    printf("%d",ans);
    return 0;
}