16 people have given me their addresses. After some struggling finding a machine that will require all of them, I obtained this diagram. This is a system that requires 16 people and says if a 4-bits number (nibble) is prime (1) or not (0).

There are 3 NOTs, 6 ANDs, 3 ORs, and 4 buffers or signal repeaters.

The longer path seems to be 7 hops long.

Some shortcuts could be taken with the ANDs when they receive a zero as one input – for practical purposes they could send their output without waiting for their another input. But it would be better to be “formal” and wait for the two inputs.

Another thing to consider, as this is executing an apparently pointless procedure, is how to get which number to use as the input for the system.