CSES - Tasks and Deadlines
  • Time limit: 1.00 s
  • Memory limit: 512 MB
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