output_description: Print the largest possible number of different letters contained in both X and
  Y.
  
  * * *
input_description: Input is given from Standard Input in the following format:
  
      
      
      N
      S
attempt: n=int(input())
  s=input()
  maxx=-
  def got(a,al):
  	for i in a:
      	if i==al:
        		return(True)
  	return(False)
  for i in range(n):
  	a=s[:i]
    	b=s[i:]
    	cnt=0
    	alp="abcdefghijklmnopqrstuvwxyz"
    	for al in alp:
      	if got(a,al) and got(b,al):
        		cnt+=1
    	maxx=max(maxx,cnt)
  print(maxx)
problem_description: 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.
samples: [{"input": "6\n    aabbca", "output": "2\n    \n\nIf we cut the string between the third and fourth letters into X = `aab` and Y\n= `bca`, the letters contained in both X and Y are `a` and `b`. There will\nnever be three or more different letters contained in both X and Y, so the\nanswer is 2.\n\n* * *"}, {"input": "10\n    aaaaaaaaaa", "output": "1\n    \n\nHowever we divide S, only `a` will be contained in both X and Y.\n\n* * *"}, {"input": "45\n    tgxgdqkyjzhyputjjtllptdfxocrylqfqjynmfbfucbir", "output": "9"}]