Devise and post here Exercise1 Algorithm (Pseudo-code) plus piece of program on Java

write program that read from input file number and output the same number to another file.

Is it possible to modify the problem so it can be solved with complexity O(n), not O(n^2)? If you have any ideas about it, post them to the topic.

Extra Points

What if we need to check if sum (or tripled number) of 3 numbers is equal to a given number, 4, 5, etc. can you do it?