#include<iostream>
#include<cstring>
#include<vector>
#include<cmath>
#include<queue> 
#include<algorithm>
#define ll long long
using namespace std;
int n,m;
int mp[200010];
struct nod{
	int st,ed;
	bool operator<(const nod&x)const{
		if(st==x.st) return ed<x.ed;
		return st<x.st;
	}
	bool operator>(const nod&x)const{return !(*this<x);}
}lis[200010];
int main(){
    freopen("dream.in","r",stdin);
    freopen("dream.out","w",stdout);
    
    priority_queue<nod,vector<nod>,greater<nod> > pq;
    scanf("%d%d",&n,&m);
    for(int i=1;i<=n;i++){
    	scanf("%d%d",&lis[i].st,&lis[i].ed);
    	pq.push(lis[i]);
	}
    for(int i=1;i<=m;i++) scanf("%d",&mp[i]);
    sort(mp+1,mp+1+m);
    int ans=0;
    for(int i=1;i<=m;i++){
    	if(pq.empty()) break;
    	if(mp[i]<pq.top().st) continue;
    	else if(mp[i]>pq.top().ed) pq.pop(),i--;
    	else ans++,pq.pop();
	}
	printf("%d",ans);
    
    return 0;
}