Laver

　 　 Nori (laver) is produced in the villages along the beaches of the Hibara Sea. All laver is formed into rectangles. When drying the laver in the sun, two sheets of laver are placed on the same rug so that the top of the first sheet is parallel to the top of the second sheet. Genm, a part-time worker, can place them parallel to each other, but he is not used to it yet, so there may be overlapping areas. The overlapped areas are not for sale, so we need to find the area of the laver that is not overlapped.

Given the position of the lower-left point, width, and height of each of the two pieces of laver placed on the same rug, write a program that outputs the area of the non-overlapping pieces of laver.

Input

The input is given in the following form.

$x_1$ $y_1$ $w_1$ $h_1$
$x_2$ $y_2$ $w_2$ $h_2$

The first line gives the coordinates of the lower left point $x_1,y_1$ ($0 \leq x_1,y_1 \leq 1,000$) and the width and height $w_1,h_1$ ($1 \leq w_1,h_1 \leq 1,000$) of the first piece of laver. The second line gives the coordinates of the lower left point $x_2,y_2$ ($0 \leq x_2,y_2 \leq 1,000$) and the width and height $w_2,h_2$ ($1 \leq w_2,h_2 \leq 1,000$) of the second piece of laver. All inputs are given as integers.

Output

Output the area of the laver in the non-overlapping area as an integer in a line.

Sample Input and Output

Sample Input 1

0 0 4 5
2 2 3 6

Sample Output 1

26

Sample Input 2

1 2 2 1
2 0 2 2

Sample Output 2

6

Sample Input 3

0 0 1 1
0 0 1 1

Sample Output 3

0

 

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