使用ifstream从文本文件中打印整数

I have an assignment where I am supposed to read multiple files containing integers (one on each line) and merge them into a output text file after sorting them. I am new to C++ so I do not know how everything works. I am testing my program with two .txt files. The first file is called fileone.txt, contains 1,2,7 (I do not know how to format this but they are all on different lines.) The second file is called filetwo.txt, and contains 1,3,5,9,10 (again every integer is on a different line).I have an assignment where I am supposed to rea