A, B, X = gets.split.map(&:to_i)

S = A * A * B

def calc(deg)
  rad = (deg * Math::PI / 180.0)

  if S / 2.0 > X
    c = Rational(B, Math.tan(rad))
    area = (c * B / 2.0) * A

    area > X
  else
    c = Rational(A, Math.cos(rad))
    h = A * Math.sin(rad)
    area = (c * h / 2.0) * A

    area <= S - X
  end
end

ok = 0
ng = 1_000_000_000_000
unit = 90 / ng.to_f

while (ok - ng).abs > 1
  mid = (ok + ng) / 2
  deg = unit * mid

  check = calc(deg)

  # p [deg, S - X, area, check, ok, ng]

  if check
    ok = mid
  else
    ng = mid
  end
end

puts ok * unit
