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 CPP):

Solution:
#include <iostream>
#include <queue>
using namespace std;

int main() {
	ios_base::sync_with_stdio(false);
	cin.tie(nullptr);

	int n, m;
	cin >> n >> m;
	vector<vector<int>> c(m);
	while (n--) {
		int a, b;
		cin >> a >> b;
		if (a <= m)
			c[a - 1].push_back(b);

	}
	int r = 0;
	priority_queue<int> q;
	for (auto& l : c) {
		for (int x : l) {
			q.push(x);
		}
		if (!q.empty()) {
			r += q.top();
			q.pop();
		}
	}
	cout << r << '\n';
	return 0;
}