Two halves
Objective
Join the two halves of the flag, which sit in different directories.
The briefing
A flag was split down the middle. The first half is in one file, the second half is in another, and they are not in the same directory.
The awkward part is that each half is on its own line. Put them together and you get a line break in the middle of the flag, which is not what you want.
Two commands are worth knowing here. Listing a tree shows you what is under a directory without walking into each one by hand. And tr can delete characters, including the newline character, if you name it.
Everything is under your home directory. Start there.
Set it up
Run this in Termux. It teaches the concept above a second time, then writes the challenge files into your home directory.
ctf start 03 The tool tells you how many files it wrote, never their names.
Then find the flag and hand it in with ctf check 03 LEARMUX{...}.
Hints
Two of them, revealed one at a time. The tool works the same way and remembers how many you have seen, so nothing is spoiled by accident.