What two pieces of information would you need in order to measure the masses of stars in an eclipsing binary system?

Afile named data.txt contains an unknown number of lines, each consisting of a single integer. write some code that creates two files, dataplus.txt and dataminus.txt, and copies all the lines of data1.txt that have positive integers to dataplus.txt, and all the lines of data1.txt that have negative integers to dataminus.txt. zeros are not copied anywhere.