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Problems

Find the area of a quadrilateral with vertices A(x1,y1), B(x2,y2), C(x3,y3), D(x4,y4).

#### Input

The coordinates of successive vertices of a quadrilateral are given in a single line. All numbers are integers, not exceeding 100 by absolute value.

#### Output

The area of a quadrilateral, rounded to integers.

Time limit 1 second
Memory limit 64 MiB
Input example #1
1 4 5 4 4 2 2 1

Output example #1
8