Problem: There are N one-off jobs available. If you take the i-th job and complete it, you will earn the reward of B_i after A_i days from the day you do it.

You can take and complete at most one of these jobs in a day.

However, you cannot retake a job that you have already done.

Find the maximum total reward that you can earn no later than M days from today.

You can already start working today.

Constraints

* All values in input are integers.
* 1 \leq N \leq 10^5
* 1 \leq M \leq 10^5
* 1 \leq A_i \leq 10^5
* 1 \leq B_i \leq 10^4

Input

Input is given from Standard Input in the following format:


N M
A_1 B_1
A_2 B_2
\vdots
A_N B_N


Output

Print the maximum total reward that you can earn no later than M days from today.

Examples

Input

3 4
4 3
4 1
2 2


Output

5


Input

5 3
1 2
1 3
1 4
2 1
2 3


Output

10


Input

1 1
2 1


Output

0

Solution (in JAVA):

Solution:
import java.util.*;

class Main{
	static int mod=1000000007;

	public static void main(String[] $){
		System.err.println();
		Scanner s=new Scanner(System.in);
		int n=s.nextInt(),days=s.nextInt();

		HashMap<Integer,ArrayList<Integer>> m=new HashMap<>();

		PriorityQueue<Integer> tasks=new PriorityQueue<>(Comparator.reverseOrder());

		for(int i=0;i<n;++i){
			int time=s.nextInt(),pay=s.nextInt();
			m.computeIfAbsent(time,o->new ArrayList<>()).add(pay);
		}


		long r=0;

		for(int i=1;i<=days;++i){
			ArrayList<Integer> l=m.get(i);
			if(l!=null)
				l.forEach(tasks::add);

			Integer task=tasks.poll();

			if(task!=null)
				r+=task;
		}

		System.out.println(r);
	}
}