we found that the student names with marks in a text file the marks decreases significantly. when exams conducted fast 4 times.The first column is the student name and the second column is marks in tests.What we need to find is which student marks decreases most often that is 3 times or 4 times. Lets take top N(=10).Those are good students if the marks decreases next time again. Then in the next step we can find what was their average % decreased. Then take top 5 of those and write their names in a text file.