Hey,

uniq
This filter removes duplicate lines from a sorted file. It is often seen in a pipe coupled with sort.
cat list−1 list−2 list−3 | sort | uniq > final.list
# Concatenates the list files,
# sorts them,
# removes duplicate lines,
# and finally writes the result to an output file.

Try this logic, hope you'll get the desired one.

Thanks
Varun.