The Corner's Share

A $6 \times 6$ image is convolved with a $3 \times 3$ filter at stride 1, twice over:

• once with valid padding (no border at all),
• once with same padding (a border of one ring of zeros).

Focus on a single pixel: the one in the top-left corner of the image. A pixel influences an output position whenever it lies anywhere inside that window — not only when it is at the window's centre.

In how many output positions does that corner pixel appear, in the valid run and in the same-padded run?