Heron's formula#926
The sides , , , and the diagonal of a convex quadrilateral are given. Determine the area of the quadrilateral using Heron's formula to calculate the area of a triangle.
In one line, five real numbers are given: , , , , (0 < a, b, c, d, f \le 100), as shown in the picture.
Print the area of the quadrilateral, calculated to decimal places.
Example 1