local a, b, x = io.read("*n", "*n", "*n")
local height = x / a / a--高さ
local diff = b - height--口までの高さ
if height >= b then
	local diag = math.sqrt(a*a + diff*diff*4)
	print(math.deg(math.atan((diff * 2) / a)))
else
	local bottom = a * height * 2 / b
	print(math.deg(math.atan(b / bottom)))
end