a, b, x = gets.split.map(&:to_i)
if x <= a * a * b / 2
  l = ((2.to_f * x) / (a * b))
  deg = (Math.atan (b / l)) * 180.0 / Math::PI
else
  v = a * a * b - x
  l = (2.to_f * v) / (a * a)
  deg = (Math.atan (l / a)) * 180.0 / Math::PI
end
puts deg

