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.*;

public class Main {
	public static void main(String[] args) {

		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int m = sc.nextInt();
		int[][] ab = new int[n][2];

		for (int i = 0; i < n; i++) {
			ab[i][0] = sc.nextInt();
			ab[i][1] = sc.nextInt();
		}
		Arrays.sort(ab, (x, y) -> x[0] - y[0]);
		PriorityQueue<Integer> q = new PriorityQueue<>((o1, o2) -> o2 - o1);

		int sum = 0;

		int index = 0;
		for (int i = 1; i <= m; i++) {
			while (index < n && ab[index][0] <= i) {
				q.add(ab[index][1]);
				index++;
			}

			if (q.size() != 0) {
				sum += (int) q.poll();
			}
		}

		System.out.println(sum);

		sc.close();

	}
}