You are given a small sorted list of numbers, and a very very very long sorted list of numbers - so long that it had to be put on a disk in different

You are given a small sorted list of numbers, and a very very very long sorted list of numbers - so long that it had to be put on a disk in different blocks. How would you find those (short list) numbers in the bigger list?
Use B+ tree to index the range of each block, and for the first string, just find the matching range by b+ tree