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)

var input=`
5 3
1 2
1 3
1 4
2 1
2 3
`;
var input = require('fs').readFileSync('/dev/stdin', 'utf8');
var arr=input.trim().split("\n").reverse();
var nm=arr.pop().split(" ").map(Number);
var obj={};
for(var i=1;i<=100000;i++)obj[i]=[];
arr.forEach(v=>{
   var ab=v.split(" ").map(Number);
   obj[ab[0]].push(ab[1]);
});
for(var k in obj){
   obj[k].sort();
}
var sum=0;
for(var i=1;i<=nm[1];i++){
   var max=0;
   var iti=null;
   for(var j=i;j>=1;j--){
      var len=obj[j].length;
      if(len==0)continue;
      if(max<obj[j][len-1]){
         max=obj[j][len-1];
         iti=j;
      }
   }
   if(max!=0){
      sum+=obj[iti].pop();
   }
}
console.log(sum);