a, b, x = gets.chomp.split(" ").map(&:to_i);

if a * a * b >= (2 * x) then
  puts  180 / Math::PI * Math.atan((a*b*b).to_f/(2*x))
else
  puts  180 / Math::PI * Math.atan(2 * (a*a*b - x).to_f/(a**3))
end
