output_description: Print the maximum possible value of floor(Ax/B) - A × floor(x/B) for a non-
  negative integer x not greater than N, as an integer.
  
  * * *
input_description: Input is given from Standard Input in the following format:
  
      
      
      A B N
attempt: #!/usr/bin/env python
  import os
  import sys
  from io import BytesIO, IOBase
  
  
  def main():
      a, b, n = map(int, input().split())
      ans = 0
      m = n
      ans = max(ans, (a * m) // b - a * (m // b))
      m = (n // b) * b - 1
      m = max(m, 0)
      # print(n,m)
      ans = max(ans, (a * m) // b - a * (m // b))
      print(ans)
  
  
  # region fastio
  
  BUFSIZE = 8192
  
  
  class FastIO(IOBase):
      newlines = 0
  
      def __init__(self, file):
          self._fd = file.fileno()
          self.buffer = BytesIO()
          self.writable = "x" in file.mode or "r" not in file.mode
          self.write = self.buffer.write if self.writable else None
  
      def read(self):
          while True:
              b = os.read(self._fd, max(os.fstat(self._fd).st_size, BUFSIZE))
              if not b:
                  break
              ptr = self.buffer.tell()
              self.buffer.seek(0, 2), self.buffer.write(b), self.buffer.seek(ptr)
          self.newlines = 0
          return self.buffer.read()
  
      def readline(self):
          while self.newlines == 0:
              b = os.read(self._fd, max(os.fstat(self._fd).st_size, BUFSIZE))
              self.newlines = b.count(b"\n") + (not b)
              ptr = self.buffer.tell()
              self.buffer.seek(0, 2), self.buffer.write(b), self.buffer.seek(ptr)
          self.newlines -= 1
          return self.buffer.readline()
  
      def flush(self):
          if self.writable:
              os.write(self._fd, self.buffer.getvalue())
              self.buffer.truncate(0), self.buffer.seek(0)
  
  
  class IOWrapper(IOBase):
      def __init__(self, file):
          self.buffer = FastIO(file)
          self.flush = self.buffer.flush
          self.writable = self.buffer.writable
          self.write = lambda s: self.buffer.write(s.encode("ascii"))
          self.read = lambda: self.buffer.read().decode("ascii")
          self.readline = lambda: self.buffer.readline().decode("ascii")
  
  
  sys.stdin, sys.stdout = IOWrapper(sys.stdin), IOWrapper(sys.stdout)
  input = lambda: sys.stdin.readline().rstrip("\r\n")
  # endregion
  
  if __name__ == "__main__":
      main()
  
problem_description: Statement
  
  Given are integers A, B, and N.
  
  Find the maximum possible value of floor(Ax/B) - A × floor(x/B) for a non-
  negative integer x not greater than N.
  
  Here floor(t) denotes the greatest integer not greater than the real number t.
samples: [{"input": "5 7 4", "output": "2\n    \n\nWhen x=3, floor(Ax/B)-A\u00d7floor(x/B) = floor(15/7) - 5\u00d7floor(3/7) = 2. This is\nthe maximum value possible.\n\n* * *"}, {"input": "11 10 9", "output": "9"}]