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**Task** | Statistics

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?

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.

Print one integer: the maximum reward.

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

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

Input:

`3`

6 10

8 15

5 12

Output:

`2`