output_description: Print number of occurrences of `ABC` in S as contiguous subsequences.
  
  * * *
input_description: Input is given from Standard Input in the following format:
  
      
      
      N
      S
attempt: lens = int(input())
  has = input()
  print(has.count("ABC"))
  
problem_description: Statement
  
  We have a string S of length N consisting of uppercase English letters.
  
  How many times does `ABC` occur in S as contiguous subsequences (see Sample
  Inputs and Outputs)?
samples: [{"input": "10\n    ZABCDBABCQ", "output": "2\n    \n\nTwo contiguous subsequences of S are equal to `ABC`: the 2-nd through 4-th\ncharacters, and the 7-th through 9-th characters.\n\n* * *"}, {"input": "19\n    THREEONEFOURONEFIVE", "output": "0\n    \n\nNo contiguous subsequences of S are equal to `ABC`.\n\n* * *"}, {"input": "33\n    ABCCABCBABCCABACBCBBABCBCBCBCABCB", "output": "5"}]