#include<bits/stdc++.h>
using namespace std;
const int N=200005;
struct st{int l,r;}a[N];
bool cmp(st a,st b){return a.l<b.l||(a.l==b.l&&a.r<b.r);}
priority_queue<int>q;
int n,m,tt,ans=0,p[N],b[N*3];
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].l,&a[i].r),b[++tt]=a[i].l,b[++tt]=a[i].r;
	for(int i=1;i<=m;i++)scanf("%d",&p[i]),b[++tt]=p[i];
	sort(b+1,b+tt+1);tt=unique(b+1,b+tt+1)-b-1;
	for(int i=1;i<=n;i++)a[i].l=lower_bound(b+1,b+tt+1,a[i].l)-b;
	for(int i=1;i<=n;i++)a[i].r=lower_bound(b+1,b+tt+1,a[i].r)-b;
	for(int i=1;i<=m;i++)p[i]=lower_bound(b+1,b+tt+1,p[i])-b;
	sort(a+1,a+n+1,cmp);sort(p+1,p+m+1);
	for(int i=1,j=1,k=1;i<=tt;i++)
	{
		while(!q.empty()&&-q.top()<i)q.pop();
		for(;a[j].l<=i&&j<=n;j++)q.push(-a[j].r);
		for(;p[k]<=i&&k<=m;k++)if(!q.empty())q.pop(),ans++;
	}
	printf("%d\n",ans);
	return 0;
}