204 - Multi Diffy

Multi Diffy

Time Limit: 1 sec


The Problem

Make a simple program that reads four variables named A, B, C, D. Calculate and print the difference between multiplication of A, B and multiplicaiton of C, D (A * B - C * D).



The Input

The input file contains 4 integer numbers A, B, C, and D (A<1000, B<1000, C<1000 and D<1000).


The Output

Output will show the difference of A * B and C * D in a separate line.


Sample Input

 10 4 5 2


Sample Output






Problem Setter: Shahin ShamS