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;
using ll = long long;

priority_queue<ll> Q;
vector<ll> v[100001];

int main()
{
    ll n,m;
    cin >> n >> m;
    for(int i=0; i<n; i++){
        ll a,b;
        cin >> a >> b;
        v[a].push_back(b);
    }

    ll ans = 0;
    for(int i=1; i<=m; i++){
        for(auto k:v[i])Q.push(k);
        if(!Q.empty()){
            ans += Q.top();
            Q.pop();
        }
    }

    cout << ans << endl;
    return 0;
}