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 PYTHON3):

Solution:
import heapq


N,M = map(int,input().split())
AB = [list(map(int,input().split())) for _ in range (N)]

AB.sort()
ans = 0 
q = []
heapq.heapify(q)
idx = 0
for i in range(1,M+1):
    while idx<N and AB[idx][0]<=i:
        heapq.heappush(q, -AB[idx][1])
        idx += 1
    if q:
        p = -heapq.heappop(q)
        ans += p
print(ans)