output_description: Print the length of the longest _ACGT string_ that is a substring of S.
  
  * * *
input_description: Input is given from Standard Input in the following format:
  
      
      
      S
attempt: S = input()
  M1 = int(S.rfind("A") - S.find("C") + 1)
  M2 = int(S.rfind("A") - S.find("G") + 1)
  M3 = int(S.rfind("A") - S.find("T") + 1)
  M4 = int(S.rfind("A") - S.find("A") + 1)
  M5 = int(S.rfind("C") - S.find("C") + 1)
  M6 = int(S.rfind("C") - S.find("A") + 1)
  M7 = int(S.rfind("C") - S.find("G") + 1)
  M8 = int(S.rfind("C") - S.find("T") + 1)
  M9 = int(S.rfind("G") - S.find("G") + 1)
  M10 = int(S.rfind("G") - S.find("C") + 1)
  M11 = int(S.rfind("G") - S.find("A") + 1)
  M12 = int(S.rfind("G") - S.find("T") + 1)
  M13 = int(S.rfind("T") - S.find("C") + 1)
  M14 = int(S.rfind("T") - S.find("A") + 1)
  M15 = int(S.rfind("T") - S.find("G") + 1)
  M16 = int(S.rfind("T") - S.find("T") + 1)
  print(max(M1, M2, M3, M4, M5, M6, M7, M8, M9, M10, M11, M12, M13, M14, M15, M16))
  
problem_description: Statement
  
  You are given a string S consisting of uppercase English letters. Find the
  length of the longest _ACGT string_ that is a substring (see Notes) of S.
  
  Here, a ACGT string is a string that contains no characters other than `A`,
  `C`, `G` and `T`.
samples: [{"input": "ATCODER", "output": "3\n    \n\nAmong the ACGT strings that are substrings of `ATCODER`, the longest one is\n`ATC`.\n\n* * *"}, {"input": "HATAGAYA", "output": "5\n    \n\nAmong the ACGT strings that are substrings of `HATAGAYA`, the longest one is\n`ATAGA`.\n\n* * *"}, {"input": "SHINJUKU", "output": "0\n    \n\nAmong the ACGT strings that are substrings of `SHINJUKU`, the longest one is\n`` (the empty string)."}]