def solve(ta, a, b)
    x = a / Math::cos(ta)
    # p Math::sin(ta)
    y = x * Math::sin(ta)
    # p [a, b, x, y]
    if y > b
        # p '!!'
        x = b / Math::sin(ta)
        y = x * Math::cos(ta)
        # p [a, b, x, y]
        # p a * y / 2
        # p a * a / Math::tan(ta) / 2
        
        return b * y / 2
    else
        return a * b - a * y / 2
    end
end
a,b,x=  gets.split.map(&:to_f)
x/=a
low, high = 0, 89.999999999
50.times do
    mid = (low + high) / 2
    if x > solve(mid * Math::PI / 180, a, b)
        high = mid
    else   
        low = mid
    end
end
puts '%.10f' % low