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 JavaScript (node.js v5.12) (judge verdict: Time Limit Exceeded)


'use strict'

function main(input) {
  input = input
    .trim()
    .split('\n')
    .map(v => v.split(' ').map(v => ~~v))
  const N = ~~input[0][0]
  const M = ~~input[0][1]
  const jobs = input.slice(1).sort((a, b) => {
    return a[0] - b[0] || a[1] - b[1] // Aの昇順、Bの降順
  })
  // let _ = input.slice(1)
  // const jobs = []
  // for (let i = 0; i < N; i++) {
  //   if (!jobs[_[i][0]]) jobs[_[i][0]] = []
  //   jobs[_[i][0]].push(_[i][1])
  // }
  // console.log(N, M, jobs) // 1000000000 = 1e9

  let ans = 0

  let day = M - 1
  let marker = 0 // day が有効な、探索の開始位置

  for (let i = day; 0 <= i; i--) {
    // console.log(i)
    let _max = 0
    let _maxind = -1
    for (let j = marker; j < N; j++) {
      if (M - i >= jobs[j][0]) {
        // console.log(M - i, jobs[j][0], jobs[j][1])
        // enable
        if (_max < jobs[j][1]) {
          _max = jobs[j][1]
          _maxind = j
        }
      } else {
        // marker = j
        break
      }
    }
    if (_max >= 1) jobs[_maxind][1] = 0 // jobs.splice(_maxind, 1)
    // console.log(_max)
    ans += _max
  }
  // console.log('----')
  console.log(ans)
  // console.log('----')

  return
}
main(require('fs').readFileSync('/dev/stdin', 'utf8'))