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 <bits/stdc++.h>
using namespace std;

int main(){
  int n, m; cin >> n >> m;
  vector<vector<int>> j(m);
  for (int i = 0; i < n; i++){
    int a, b; cin >> a >> b;
    if (a <= m){
      a--;
      j.at(a).push_back(b);
    }
  }
  priority_queue<int> q;
  int64_t ans = 0;
  for (int i = 0; i < m; i++){
    for (int k : j.at(i)){
      q.push(k);
    }
    if (q.size()){
      int l = q.top();
      q.pop();
      ans += l;
    }
  }
  cout << ans << endl;
}