Fly Monkey is a well-known program of the circus, which is performed by the beautiful and lovely monkey Pipi. In the program of Fly Monkey, there are two long steel wires in air. Pipi is initially located on one of the wires, and her objective is reaching another wire. Pipi must first crawl over the wire from her initial position by some distance, and then jump to some position of another wire. Since Pipi moves quite fast, the trace of her jumping can be considered as a straight line. To prevent from dangers, Pipi tends to shorten her jumping distance, while cannot crawl by more than distance d in advance to save the time. In this conditions, how long Pipi must jump at least?

There is only one line for each test case, which contains a real number. Three digits after decimal point are preserved by rounding.