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Problem B
Rectangle Area

Given diagonal corners of a rectangle with sides parallel to the $X$ and $Y$ axes, compute the area of the rectangle.

$\includegraphics[width=0.75\textwidth ]{area}$

Input

The single line of input contains four real numbers $x 1$ , $y 1$ , $x 2$ and $y 2$ ( $| x 1 |, | y 1 |, | x 2 |, | y 2 | \leq 100.0$ ), where $(x 1, y 1)$ and $(x 2, y 2)$ are diagonal corners of a rectangle with sides parallel to the $X$ and $Y$ axes. The rectangle is guaranteed to have an area greater than $0.01$ .

Output

Output a single line with a single real number, which is the area of the given rectangle. This number must be accurate to within $10^{- 2}$ absolute or relative error.

Sample Input 1	Sample Output 1
0.0 0.0 3.0 4.0	12.000

Sample Input 2	Sample Output 2
5.2 -4.64 -3.47 2.2	59.303

Problem BRectangle Area

Input

Output

Problem B
Rectangle Area