You will be given a definition of a task first, then some input of the task.
The task is to generate the correct answer for a given math problem.

Problem: a contractor undertook to do a piece of work in 18 days . he employed certain number of laboures but 9 of them were absent from the very first day and the rest could finish the work in only 6 days . find the number of men originally employed ?
Output:
4.5