Tea Garden#418
Tea grows on a triangular hillside. A small teahouse stands somewhere strictly inside it, and three straight paths cross the hillside through the teahouse — each path parallel to one of the three sides.
The paths leave three triangular beds of tea, with areas S_1, S_2 and S_3. How large is the hillside?
One line contains three positive real numbers S_1, S_2 and S_3 (0 < S_i \le 1000).
Print the area of the hillside with digits after the decimal point.
Example 1