#include <bits/stdc++.h>
#define _NVQ ""
#define int long long
#define pii pair<int,int>
#define fi first
#define se second
using namespace std;
int n,m,c[100005];
pii sv[100005];
int32_t main()
{
// if(fopen(_NVQ".INP","r"))
// {
// freopen(_NVQ".INP","r",stdin);
// freopen(_NVQ".OUT","w",stdout);
// }
ios_base::sync_with_stdio(0);
cin.tie(0);cout.tie(0);
cin >> n >> m;
for (int i=1;i<=n;++i)
{
cin >> sv[i].fi >> sv[i].se;
}
for (int i=1;i<=m;++i)
{
cin >> c[i];
}
sort(c+1,c+m+1);
sort(sv+1,sv+n+1);
int id=1;
priority_queue <int,vector<int>,greater<int>> pq;
vector <int> v;
for (int i=1;i<=m;++i)
{
while (sv[id].fi <= c[i] && id <= n)
{
pq.push(sv[id].se);
++id;
}
if (pq.empty()) continue;
int x = pq.top(); pq.pop();
auto beo = upper_bound(v.begin(),v.end(),x);
if (beo==v.end()) v.push_back(x);
else *beo = x;
}
cout << v.size();
}
