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 <string.h>
int main()
{   int  n,i,j,ans=0,cnt=0;
    char s[101];
    scanf("%d%s",&n,s);
    for(i=1;i<n-1;i++){
    int x[27]={0},
        y[27]={0};
        for(j=0;j<i;j++){
            x[(s[j]-'a')]=1;     
        }
        for(j=n-1;j>=i;j--){
            y[(s[j]-'a')]=1;
        }
        int k;
        for(k=0;k<26;k++){
            if(x[k]==1&&y[k]==1){
                cnt++;
            }
        }
        if(cnt>ans){
            ans=cnt;
            
        }
        cnt=0;
    }
    printf("%d",ans);
    return 0;
}