0.3 Optimal Flagstone Paving

Score: 10pts

Time Limit: 2.00 sec

In the bustling city of Urbana, the Plaza Promenade takes the shape of a rectangular area measuring n × m meters. To commemorate a special occasion, the city plans to adorn the plaza with square granite flagstones, each having sides of length a × a meters.

While exceeding the boundaries of the Plaza Promenade is acceptable, the entire plaza must be covered using complete flagstones. What is the smallest possible number of flagstones needed to accomplish this paving task?

While exceeding the boundaries of the Plaza Promenade is acceptable, the entire plaza must be covered using complete flagstones. What is the smallest possible number of flagstones needed to accomplish this paving task?

Constraints

Constraints have been provided in the Input format

Input Format

The input contains three positive integer numbers in the first line: n, m and a (1 ≤ n, m, a ≤ 10^9)

Output Format

Write the needed number of flagstones.

Example 1

Input:

6 6 4

Output:

4

Explanation:

Example is self explanatory

6 6 4

Output:

4

Explanation:

Example is self explanatory