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: Wrong Answer)

function main(input) {
    var args = input.trim().split("\n");
    var info = args[0].split(" ").map((v) => parseInt(v));
    var N = info[0];
    var M = info[1];
    var jobs = args.filter((v, i) => i !== 0).map((v) => {
        return v.split(" ").map(v2 => parseInt(v2));
    });

    jobs.sort((a, b) => {
        return a[1] > b[1] ? -1 : 1;
    });

    var result = 0;
    while(M !== 0 && jobs.length > 0) {
        var job = null;
        while (jobs.length > 0) {
            job = jobs.shift();
            if (job[0] > M) continue;
            result += job[1];
            break;
        }
        M--;
    }

    console.log(result);
}

main(require("fs").readFileSync("/dev/stdin", "utf8"));