| You want to write an image detection system that is able to recognize |
| different geometric shapes. In the first version of the system you settled |
| with just being able to detect filled squares on a grid. |
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| You are given a grid of **N**×**N** square cells. Each cell is either white or |
| black. Your task is to detect whether all the black cells form a square shape. |
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| ### Input |
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| The first line of the input consists of a single number **T**, the number of |
| test cases. |
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| Each test case starts with a line containing a single integer **N**. Each of |
| the subsequent **N** lines contain **N** characters. Each character is either |
| "." symbolizing a white cell, or "#" symbolizing a black cell. Every test case |
| contains at least one black cell. |
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| ### Output |
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| For each test case **i** numbered from 1 to **T**, output "Case #**i**: ", |
| followed by YES or NO depending on whether or not all the black cells form a |
| completely filled square with edges parallel to the grid of cells. |
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|
| ### Constraints |
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| 1 ≤ **T** ≤ 20 |
| 1 ≤ **N** ≤ 20 |
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| ### Example |
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| Test cases 1 and 5 represent valid squares. Case 2 has an extra cell that is |
| outside of the square. Case 3 shows a square not filled inside. And case 4 is |
| a rectangle but not a square. |
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