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Score : $100$ points

### Problem Statement

Given is a $2 \times 2$ matrix $A = \begin{bmatrix} a & b \\ c & d \end{bmatrix}$.
The determinant of $A$ can be found as $ad-bc$.
Find it.

### Constraints

• All values in input are integers.
• $-100 \le a, b, c, d \le 100$

### Input

Input is given from Standard Input in the following format:

$a$ $b$
$c$ $d$


### Output

Print the answer as an integer.

### Sample Input 1

1 2
3 4


### Sample Output 1

-2


The determinant of $\begin{bmatrix} 1 & 2 \\ 3 & 4 \end{bmatrix}$ is $1 \times 4 - 2 \times 3 = -2$.

### Sample Input 2

0 -1
1 0


### Sample Output 2

1


### Sample Input 3

100 100
100 100


### Sample Output 3

0