Question: You have X-by-Y rectangular field and you want to plant trees. There are k parts in the field where you cannot plant anything. And, every tree requires at least w-square-meter. Write a program, that defines the maximum number of trees that you can plant.

Input specification: You will be given four integers in the beginning,

• the width of the field (X)
• the length of the field (Y)
• the width required for every tree (w)
• the number of objects in the field (k)

Output specification: Show one integer (the number of trees that can be planted).