Tasks and Deadlines

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?

Input

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.

Output

Print one integer: the maximum reward.

Constraints

$1 \le n \le 2$ \cdot 10^5$

$1 \le a,d \le 10^6$

Example

Input

3
6 10
8 15
5 12

Output

2