import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.util.*;
public class JOI_19_exhibition{
public static void main(String[] args) throws Exception{
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
StringTokenizer st = new StringTokenizer(br.readLine());
int n = Integer.parseInt(st.nextToken());
int m = Integer.parseInt(st.nextToken());
int[][]already_calculated = new int[n][m];
Map<List<Integer>, Integer>memoi = new HashMap<>();
Picture[] pictures = new Picture[n];
int[] frames = new int[m];
for(int i = 0; i < n; i++){
for(int j = 0; j < m; j++){
already_calculated[i][j] = -1;
}
}
for(int i = 0; i < n; i++){
st = new StringTokenizer(br.readLine());
pictures[i] = new Picture(Integer.parseInt(st.nextToken()), Integer.parseInt(st.nextToken()));
}
for(int i = 0; i < m; i++){
frames[i] = Integer.parseInt(br.readLine());
}
Arrays.sort(pictures, new PictureComp());
Arrays.sort(frames);
System.out.println(recursive(0, 0, pictures, frames, memoi));
}
public static int recursive(int picture_index, int frame_index, Picture[] pic, int[]fra, Map<List<Integer>, Integer> memoi) {
if ((picture_index >= pic.length) || (frame_index >= fra.length)) {
return 0;
}
List<Integer> ordered_pair = new ArrayList<>();
ordered_pair.add(picture_index);
ordered_pair.add(frame_index);
if(memoi.containsKey(ordered_pair) && !(memoi.get(ordered_pair) == -1)){
return memoi.get(ordered_pair);
}
if(fra[frame_index] >= pic[picture_index].size){
// choosing both frame and picture and moving the pointers.
memoi.put(ordered_pair,1 + recursive(picture_index + 1, frame_index + 1, pic, fra, memoi));
return memoi.get(ordered_pair);
}else {
// move to the next indices on either and see which is better.
int second_ans = Math.max(recursive(picture_index +1, frame_index, pic, fra, memoi), recursive(picture_index, frame_index + 1, pic, fra, memoi));
memoi.put(ordered_pair, second_ans);
return memoi.get(ordered_pair);
}
}
}
class Picture{
int size;
int value;
public Picture(int a, int b){
this.size = a;
this.value = b;
}
}
class PictureComp implements Comparator<Picture> {
public int compare(Picture p1, Picture p2){
if(p1.value == p2.value){
return p1.size - p2.size;
}
return p1.value-p2.value;
}
}
