Heron
Very easy
Execution time limit is 1 second
Runtime memory usage limit is 128 megabytes
![](https://static.e-olymp.com/content/53/53de119ca21346bc658a51b2e42f1851c11e9ed9.jpg)
The sides and the diagonal of a convex quadrilateral are given. Find the area of a quadrilateral, using the Heron’s formula that calculates the area of a triangle.
Input
In one line five real numbers are given: . They are the lengths of segments as shown in the picture.
Output
Print the area of a quadrilateral with decimal digits.
Examples
Input #1
Answer #1
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