import strutils, sequtils, algorithm, future

{.warning[SmallLshouldNotBeUsed]: off.}

when isMainModule:
  var
    b = stdin.readLine.split.map(parseFloat)
    r = (b[2] - b[1]) / (b[1] - b[0])
    d = b[1] - r*b[0]
  if r*b[2] + d == (r*b[2] + d).int.float:
    echo((r*b[2] + d).int)
  else:
    echo((r*b[2] + d + 1e-8).int)