Tasks and Deadlines

You have to process $nn$ 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 $d-fd-f$ where $dd$ is its deadline and $ff$ is your finishing time. (The starting time is $00$, and you have to process all tasks even if a task would yield negative reward.)

What is your maximum reward if you act optimally?

Input

The first input line has an integer $nn$: the number of tasks.

After this, there are $nn$ lines that describe the tasks. Each line has two integers $aa$ and $dd$: the duration and deadline of the task.

Output

Print one integer: the maximum reward.