input = gets.chomp.split(" ").map(&:to_i)
a = input[0]
b = input[1]
x = input[2]

if x <= a*a*b.to_f/2
  h = x*2 / (a*b).to_f
  angle = Math.atan(b/h)
else
  x = a*a*b - x
  h = x * 2 / (a*a).to_f
  angle = Math.atan(h/a)
end
angle = angle * 180 / Math::PI
puts angle
