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 = [i for i in input()]

max = 0

for i in range(1, n-1):
    a = set(s[:i])
    b = set(s[i:])

    print(a & b)
    
    if max < len(a & b):
        max = len(a & b)
print(max)


N = int(input())
S = list(input())
 
m = 0
for i in range(1, N - 1):
    a = set(S[:i])
    b = set(S[i:])
    if m < len(a & b):
        m = len(a & b)
 
print(m)