307 - Multi Diffy Again

Multi Diffy Again

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

Input file contain a series of line, each line contain 4 integer numbers A, B, C, and D (A<1000, B<1000, C<1000 and D<1000). Input is terminated by EOF.


The Output

For each line of input, output will show the difference between A * B and C * D in a separate line.


Sample Input

10 4 5 2

12 13 14 15

15 14 13 12


Sample Output









Problem Setter: Shahin ShamS