import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.NavigableSet;
import java.util.Scanner;
import java.util.SortedSet;
import java.util.Stack;
import java.util.TreeMap;
import java.util.TreeSet;

/*
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 * To change this template file, choose Tools | Templates
 * and open the template in the editor.
 */
/**
 *
 * @author Vendetta
 */
public class Main {

    static TreeMap<Integer, ArrayList<Integer>> map;

    public static void main(String args[]) {
        Scanner sc = new Scanner(System.in);
        int N, H, v, t, total, T, V;
        ArrayList<Integer> list;
        TreeSet<Integer> timeLine = new TreeSet();
        while (sc.hasNext()) {
            map = new TreeMap<>();
            N = sc.nextInt();
            H = sc.nextInt();
            for(int i=1;i<=H;i++){
                timeLine.add(i);
            }
            total = 0;
            for (int i = 0; i < N; i++) {
                v = sc.nextInt();
                total += v;
                t = sc.nextInt();
                list = map.get(v);
                if (list == null) {
                    list = new ArrayList<>();
                }
                list.add(t);
                map.put(v, list);
            }
            T = 0;
            V = 0;
            Integer temp,lower;
            for (Integer cost : map.descendingKeySet()) {
                list = map.get(cost);
                Collections.sort(list);
                for(int i=0;i<list.size() && T< H;i++){
                    temp= list.get(i);
                    lower = timeLine.floor(temp);
                    if(lower!=null){
                        V+=cost;
                        T++;
                        timeLine.remove(lower);
                    }
                }
            }
            System.out.println((total - V));
        }
    }
}