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.
n = int(input())
s = list(input())

ans = 0
for i in range(1,n-1):
    ans = max(ans, len(list(set(s[:i]) & set(s[i:]))))
    print(set(s[:i]) & set(s[i:]))
print(ans)
n = int(input())
s = list(input())

ans = 0
for i in range(1,n-1):
    ans = max(ans, len(list(set(s[:i]) & set(s[i:]))))
print(ans)