The sides a,b,c,d and the diagonal f of a convex quadrilateral are given. Find the area of a quadrilateral, using the Heron’s formula that calculates the area of a triangle.
In one line five real numbers are given: a,b,с,d,f (0<a,b,c,d,f≤100). They are the lengths of segments as shown in the picture.
Print the area of a quadrilateral with 4 decimal digits.