Given a set of intervals in format [startTime, endTime, period], indicating that a task need to be completed between startTime to endTime and period indicates amount of time required to complete the task.
A task can be completed in discontinuous time.
Multiple tasks can be done at same time. Find the minimum time required to complete all tasks.


Example:
[1,5,2]
[2,5,2]
[1,3,2]
[6,6,1]
[5,9,3]
[8,9,2]


Minimum time will be 5 as we can pick [2,3] by which all first 3 taks will be done and then, pick [6] for completing 4th task and 1 unit of 5th task. Now, pick [8,9] for remaining work of 5th task and to complete last task.


Constraints:
Number of Tasks<=1e3
Interval Times<=1e6


This is a question from online assessment of some company, which is completed now. Could not get any idea other than greedy which didn't work.