Pond Digging (II)

Time Limit: 1 sec

**The Problem**

You all may be remembered **Mrs. Rahman** who wanted to dig a pond in her rectangular plot. After talking **Ali** suddenly a thought came to her mind what will be the area of the **edge**. She made a way to calculate this. Can you find the way which she used to calculate the area of **edge**?

**The Input**

The input file contains four integer numbers length, **L** (**L**<=500) and width, **W** (**W**<=400) of the plot and length, **l** (**l**<=5) and width, **w** (**W**<=4) of the border.

**The Output**

The output will show the area of the **edge** in a separate line.

**Sample Input**

100 80 3 2

**Sample Output**

832

Problem Setter: Samia Safa Ahmed

Special thanks to Shahin ShamS