#include<bits/stdc++.h>
using namespace std;
struct mj{
	int l,r;
}a[200010];
int n,m,b[1000010]={},ans=0;
bool cmp(mj x,mj y)
{
	if(x.r==y.r)
	{
		return x.l<y.l;
	}
	else
	{
		return x.r<y.r;
	}
}
int main()
{
	freopen("dream.in","r",stdin);
    freopen("dream.out","w",stdout);
	cin>>n>>m;
	for(int i=1;i<=n;i++)
	{
		cin>>a[i].l>>a[i].r;
	}
	for(int i=1;i<=m;i++)
	{
		int x;
		cin>>x;
		b[x]++;
	}
	sort(a+1,a+n+1,cmp);
	for(int i=1;i<=n;i++)
	{
		for(int j=a[i].l;j<=a[i].r;j++)
		{
			if(b[j]>0)
			{
				ans++;
				b[j]--;
				break;
			}
		}
	}
	cout<<ans;
	return 0;
}