PI = Math::PI
A, B, X = gets.split.map(&:to_f)
capa = A**2 * B
ans = 0
if X > capa/2
  # a*(a*?/2) = 水筒キャパ - 水
  n = 2 * (capa - X)/(A**3)
  ans = (Math.atan(n)).abs * 180/PI
else
  # a*(b*?/2) = 水
  n = 2 * X/(A*B**2)
  ans = 90 - (Math.atan(n)).abs * 180/PI
end
p ans