2x2 Matrix Determinant

Given four integers a, b, c, and d, compute the determinant of the 2x2 matrix:

$$\begin{vmatrix} a & b \\ c & d \end{vmatrix} = a \times d - b \times c$$

inputFormat

The input consists of a single line containing four space-separated integers: a, b, c, and d.

outputFormat

Output a single integer which is the value of the determinant, computed as $$a \times d - b \times c$$.

sample

1 2 3 4

-2