Vinnimobil - the latest high-tech, environmentally ultrapure vehicle, on linden honey. White honey is known to be very energetically favorable fuel: its consumption is \textbf{1} barrel per mile. Buck vinnimobilya just holds a barrel of honey. Carry honey in other containers is prohibited: there is a danger that the driver it is simply going to eat. But allowed to pour the honey from the tank on the roadside, then to assemble it and cram back (most interestingly, no losses). Winnie wants to get on vinnimobile to Piglet, who lives at a distance of \textbf{x} miles, spending, of course, the minimum amount of honey. So how many barrels will spend Winnie? \InputFile In the input file contains a real number \textbf{x} (\textbf{0} ≤ \textbf{x} ≤ \textbf{5}). \OutputFile Display the number of barrels of honey, Winnie the necessary, up to three decimal places.