Six Stages Back to the Pixels

A photograph is pushed through six stages, in this order:

stage	operation
1	convolution, $3 \times 3$ kernel, stride $1$ , "same" padding
2	convolution, $3 \times 3$ kernel, stride $1$ , "same" padding
3	max pooling, $2 \times 2$ window, stride $2$
4	convolution, $3 \times 3$ kernel, stride $1$ , "same" padding
5	max pooling, $2 \times 2$ window, stride $2$
6	convolution, $3 \times 3$ kernel, stride $1$ , "same" padding

Now pick one single unit near the middle of the map that stage 6 produces — near the middle, so that nothing it depends on runs off the edge of the photograph.

How large a square region of the original photograph can influence that one unit's value?

Six Stages Back to the Pixels

Hints