Advent Challenge 5: Move the presents to the transport docks!
Haskell, 26 bytes



a#s=[x|r&lt;-s,x&lt;-a,elem x r]


Try it online! Example usage: [1,2,3,4,5,6,7] # [[1,2,3],[4,5,6,7]] yields [1,2,3,4,5,6,7].