In honor of the birth of an heir Tutti royal chef has prepared a huge cake, that was put on the table for Three Fat Man. The first fat man can eat the cake by himself for t₁ hours, second - for t₂ hours, and the third - for t₃ hours.

   For what time can the cake be eaten simultaneously by all three fat men?

   Input

   One line contains three positive integers t₁, t₂ and t₃, each of them is no more than 10000.

   Output

   Print the time in hours during which the cake can be eaten simultaneously by three fat men. Print the result with 2 digits after the decimal point.