B. Tasks and Deadlines
time limit per test
2 seconds
memory limit per test
1024 megabytes
input
standard input
output
standard output

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 $$$n$$$ ($$$1 \leq n \leq 2\cdot 10^5$$$): the number of tasks.

After this, there are $$$n$$$ lines that describe the tasks. Each line has two integers $$$a$$$ and $$$d$$$ ($$$1 \leq a,d \leq 10^6$$$): the duration and deadline of the task.

Output

Print one integer: the maximum reward.

Example
Input
3
6 10
8 15
5 12
Output
2