Problem:
Score : 400 points

Problem Statement

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.

Sample Input 1

3 4
4 3
4 1
2 2

Sample Output 1

5

You can earn the total reward of 5 by taking the jobs as follows:

Take and complete the first job today. You will earn the reward of 3 after four days from today.

Take and complete the third job tomorrow. You will earn the reward of 2 after two days from tomorrow, that is, after three days from today.

Sample Input 2

5 3
1 2
1 3
1 4
2 1
2 3

Sample Output 2

10

Sample Input 3

1 1
2 1

Sample Output 3

0

Solution in PyPy3 (2.4.0) (judge verdict: Time Limit Exceeded)

import sys
from collections import deque

def main():
    input = sys.stdin.readline
    N, M = map(int, input().split())
    q = deque()
    for _ in range(N):
        a, b = map(int, input().split())
        if a > M:
            continue
        q.append((a, b))

    ans = 0
    cnt = 1
    while cnt <= M:
        q_ = deque()
        max_a, max_b = 0, 0
        while q:
            a, b = q.pop()
            if a > cnt:
                q_.append((a, b))
                continue
            elif b > max_b:
                q_.append((max_a, max_b))
                max_a, max_b = a, b
            else:
                q_.append((a, b))

        ans += max_b
        cnt += 1
        q = q_


    return ans


if __name__ == '__main__':
    print(main())