You have to process $n$ tasks. Each task has a duration and a deadline, and you will process the tasks in some order one after another. Your reward for a task is $d-f$ where $d$ is its deadline and $f$ is your finishing time. (The starting time is $0$ , and you have to process all tasks even if a task would yield negative reward.)
What is your maximum reward if you act optimally?
The first input line has an integer $n$ : the number of tasks.
After this, there are $n$ lines that describe the tasks. Each line has two integers $a$ and $d$ : the duration and deadline of the task.
Print one integer: the maximum reward.