a, b, x = gets.split.map(&:to_f)
h = x / (a ** 2)
air_h = b - h
water_s = h * a
air_s = air_h * a
top = 90.0
bottom = 0.0

while top - bottom > 0.00000005
    angle = (top + bottom) / 2.0
    height = a * Math.tan(Math::PI * angle / 180)
    if height <= b  # 液面が壁に触れる 
        if air_s > a * height / 2  # 溢れない
            bottom = angle
        else
            top = angle
        end
    else  # 液面が底に触れる
        water_angle = 90.0 - angle
        if water_s < b * b * Math.tan(Math::PI * water_angle / 180) / 2  # 溢れない
            bottom = angle
        else
            top = angle
        end
    end
end
puts bottom
