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++14 (GCC 5.4.1) (judge verdict: Accepted)

#include<stdio.h>
#include<string.h>
#include<algorithm>
using namespace std;
char str[120];
int a[27],b[27];
int main()
{
    int n;
    scanf("%d%s",&n,str);
    int num1,num2,num3,num=0;
    for(int i=0;i<n;i++)
    {
        num1=0,num2=0,num3=0;
        memset(a,0, sizeof(a));
        for(int j=0;j<=i;j++)
        {
            if(a[str[j]-'a']==0)
            {
                num1++;
                a[str[j]-'a']=1;
            }
        }
        memset(b,0, sizeof(b));
        for(int j=i+1;j<n;j++)
        {
            if(b[str[j]-'a']==0)
            {
                num2++;
                b[str[j]-'a']=1;
            }
        }
        for(int i=0;i<27;i++)
            if(a[i]==b[i]&&a[i]!=0)
                num3++;
        num=max(num,num3);
    }
    printf("%d",num);
    return 0;
}