A group of n red pirates and a group of n blue pirates have a shared treasure chest and one unique lock and key for each pirate. Using hardware that is probably already lying around their two ships, they want to protect the chest so that any pair of pirates, one red and one blue, can open the chest using their two locks and keys, but no group of red or blue pirates can open the chest without

having at least one pirate from the other group. How do they set this up?

What will be an ideal response?

The red pirates link their locks together in a chain and wrap that chain through
a latch on the chest that is big enough to let locks slide through it. Likewise, the blue
pirates link their locks together in a chain and wrap that chain through the same latch.
Now, to open the chest, they need one red pirate to open the chain of red-pirate locks and
they need one blue pirate to open the chain of blue-pirate locks.