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: Runtime Error)

function Main(input) {
	var idata = input.split(/\n/);
	var b = [];
    var kensuu = idata[0].split(" ")[0];
    var nissuu = idata[0].split(" ")[1];
    var houshuu = 0;
	for(i=0;i<kensuu;i++){
		b[i]=idata[i+1].split(" ");
    }
	//仕事を報酬順に並べ替え
	b.sort(high);
	function high(a,b){
	   return a[1]<b[1];
	}
	//仕事選び
	for(day=0;day<nissuu;day++){
		for(let j=0;j<b.length;j++){
			if(nissuu-day>=b[j][0]){
				houshuu += parseInt(b[j][1]);
				b.splice(j,1);
				break;
			}
		}
	}
	console.log(houshuu);
}    

//*この行以降は編集しないでください（標準入出力から一度に読み込み、Mainを呼び出します）
Main(require("fs").readFileSync("/dev/stdin", "utf8"));