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

Example Output

2