a,b,x = gets.split(" ").map(&:to_i)
s = x.to_f/a.to_f
answer = 0
if s > (a*b / 2)
  t = (((2*b.to_f)/(a.to_f))-((2*x.to_f)/(a*a*a.to_f)))
  answer = (Math.atan(t) * 180) / Math::PI
elsif s <= (a*b / 2)
  u = (a*b*b.to_f)/(2*x.to_f)
  answer = (Math.atan(u) * 180) / Math::PI
end

puts answer