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.ArrayList;
import java.util.List;
import java.util.ListIterator;
import java.util.PriorityQueue;
import java.util.Scanner;

public class Main {

	public static void main(String[] args) {

		try (Scanner sc = new Scanner(System.in)) {

			int n = sc.nextInt();
			int m = sc.nextInt();
			// アルバイトできる日、それぞれに日当のリストを持つ
			List<List<Integer>> jobs = new ArrayList<>(m);
			for(int i = 0 ; i < m ; i++) {
				jobs.add(new ArrayList<>());
			}

			// アルバイトを順番にループ
			// ギリギリ期日までに報酬が得られるものを全てListに積む
			for(int i = 0 ; i < n ; i++) {
				int a = sc.nextInt();
				int b = sc.nextInt();
				// 期日までに報酬が得られないものはスルー
				if(m < a) {
					continue;
				}
				List<Integer> rewardList = jobs.get(m - a);
				rewardList.add(b);
			}

			// 優先度付きキューを生成(報酬の大きいものを優先)
			PriorityQueue<Integer> q = new PriorityQueue<>((o1, o2) -> {
				return Integer.compare(o2, o1);
			});

			long value = 0;
			// 期日から1日ずつ前にループ
			for(ListIterator<List<Integer>> ite = jobs.listIterator(jobs.size()) ; ite.hasPrevious() ;) {
				// その日に可能なアルバイトをキューに積む
				for(Integer v : ite.previous()) {
					q.add(v);
				}
				// もっとも優先度の高い報酬を取り出す
				if(!q.isEmpty()) {
					value += q.poll();
				}
			}
			System.out.println(value);

		}
	}

}