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(), M = sc.nextInt();
		int[][] A = new int[N][2];
		for(int i = 0; i < N; i++) {
			A[i][0] = sc.nextInt();
			A[i][1] = sc.nextInt();
		}
		Arrays.sort(A, (x,y) -> x[0]-y[0]);
		long ans = 0;
		int p = 0;
		PriorityQueue<Integer> pq = new PriorityQueue<>(Collections.reverseOrder());
		for(int i = 1; i <= M; i++) {
			for(int j = p; j < N; j++) {
				if(A[j][0] <= i)
					pq.offer(A[j][1]);
				else {
					p = j;
					break;
				}
				if(j == N-1)
					p = N;
			}
			if(pq.size() > 0)
				ans += pq.poll();
		}
		System.out.println(ans);
	}

}