How can I access each elements of an one contour?

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i am new in OpenCV. I have the following problem. suppose I retrieved a contour from image. It is look like this: square[0] and the size of square[0] is [1×4]. suppose the elements are look like this: [2,3;4,5;6,7;1,2]

How can I access each element. As for example How can I retrieve only 2?