#include<cmath>
#include<cstdio>
#include<cstring>
#include<iostream>
#include<algorithm>
#include<cstdlib>
#include<queue>
#define maxn 200010
using namespace std;
priority_queue<int>q;
int n,m,z[maxn],ans,ld=1;
struct hs{int x,y;}a[maxn];
bool bk(hs a1,hs a2){return a1.x<a2.x;}
int main(){
	freopen("dream.in","r",stdin);
	freopen("dream.out","w",stdout);
	scanf("%d%d",&n,&m);
	for(int i=1;i<=n;i++)scanf("%d%d",&a[i].x,&a[i].y);
	for(int i=1;i<=m;i++)scanf("%d",&z[i]);
	sort(a+1,a+1+n,bk);sort(z+1,z+1+m);
	for(int i=1;i<=m;i++){
		while(ld<=n&&a[ld].x<=z[i])q.push(-a[ld].y),ld++;
		while(q.size()){
			if(-q.top()<z[i])q.pop();
			else break;
		}
		if(q.size())ans++,q.pop();
	}
	printf("%d\n",ans);
	return 0;
}