Description

On the first day of school, the teacher assigned all the homework. Each assignment will earn credits only if it is submitted within the specified deadline. The deadlines and credits for each assignment may vary. For example, if an assignment is worth $10$ credits and must be submitted within $6$ days, then to earn those $10$ credits, the assignment must be submitted by the end of the 6th day.

Each assignment takes exactly one day to complete. For instance, suppose there are 7 assignments with their respective deadlines and credits as follows:

The maximum credits that can be earned is $15$, with one possible order of completing the assignments being $2,6,3,1,7,5,4$. Note that there may be other methods.

Your task is to find an order of completing the assignments that maximizes the total credits earned.

Input Format

The first line contains an integer $N$, representing the number of assignments;

The next $N$ lines each contain two integers: the first integer indicates the deadline of the assignment, and the second integer indicates the credits for that assignment.

Output Format

Output an integer representing the maximum credits that can be earned. It is guaranteed that the answer does not exceed the range of int in C/C++.

Sample 1

7
1 6
1 7
3 2
3 1
2 4
2 5
6 1

15

Constraints & Hints

For $20\%$ of the data, $N \leq 10^3$;

For $40\%$ of the data, $N \leq 10^4$;

For $60\%$ of the data, $N \leq 10^5$;

For $100\%$ of the data, $N \leq 10^6$, and the deadlines for all assignments are less than $7\times 10^5$.