在上图中，请注意中心和第3环未填充。

In the illustration above, notice that the center and 3rd ring are not filled.

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请注意，从中心开始数的第三个弧未填充。

Notice that the third arc from the center is not filled.

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请注意，从中心开始数的第三个弧未填充。

Notice that the third arc from the center is not filled.

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