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;
	char S[101];
	scanf("%d",&N);
	int i,ans=0;
	scanf("%s",S);				//ここ！文字列読み取りだけならこれでよい
	
	int cut = 1;
	int memo=0;
	int lFlag=0,rFlag=0;
	
	while(cut <= N){
		memo = 0;
		char target; // 'a' = 97
		for(target='a';target<='z';target++){
			for(i=0;i<cut;i++){
				if(S[i] == target){
					lFlag = 1;
				}
			}
			for(i=cut;i<N;i++){
				if(S[i] == target){
					rFlag = 1;
				}
			}
			if(lFlag==1 && rFlag == 1){
				memo++;
			}
			lFlag=0;rFlag=0;
		}
		if(memo >= ans){
			ans = memo;
		}
		cut++;
	}
	
	printf("%d",ans);
	return 0;}