a, b, x = gets.split.map(&:to_f)
water = x / a
air = a * b - water

if water > air
    define_method(:overflow){|degree|
        air < a * a * Math::tan(degree * Math::PI / 180) / 2.0
    }
else
    define_method(:overflow){|degree|
        water > b * b * Math::tan((90 - degree) * Math::PI / 180) / 2.0
    }
end

flat = 0.0
steep = 90.0
while steep - flat > 0.0000001
    mid = (flat + steep) / 2.0
    if overflow(mid)
        steep = mid
    else
        flat = mid
    end
end

puts flat
