Block Checkerboard
Given m, n, and k, print a checkerboard with m block rows and n block columns. Each block has size k x k characters.
Input
- One line containing three positive integers m, n, and k.
Output
- A block whose block-row index plus block-column index is even is filled with *; otherwise it is filled with ..
Constraints
- 1 <= m, n <= 30
- 1 <= k <= 10
Example
Input
3 4 2
Output
**..**..
**..**..
..**..**
..**..**
**..**..
**..**..
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