A rectangular room without any doors or windows has a width of $$b$$ meters, a length of $$l$$ meters and a height of $$h$$ meters. How many rolls of wallpaper having a width of $$f$$ meters and a length of $$h$$ meters are needed to completely cover the room, except for the floor and the ceiling?

Input

In the following order, the real-valued numbers $$b$$, $$l$$, $$h$$ and $$f$$, each on a separate line.

Output

The minimal number of wallpaper rolls needed to completely cover the room. Only complete rolls of wallpaper are for sale.

Example

Input:

3.14
2.72
2.34
1.11

Output:

11