#include<bits/stdc++.h>
using namespace std;
#define S second
#define F first
#define ll long long
//#define int long long
//#pragma GCC optimize("Ofast, unroll-loop")
//#pragma GCC target("avx,avx2")
#pragma GCC optimize("O3")
const int inf=0x3f3f3f3f;
const ll inff=0x3f3f3f3f3f3f3f3f;
//const int X=1000000007;
const int X=998244353;
pair<int,int> p[100005];
int f[100005], id[100005], lb[100005], mx=0, mn=inf;
signed main(){
ios::sync_with_stdio(0), cin.tie(0);
int n, m;
cin >> n >> m;
for(int i=0 ; i<n ; i++) cin >> p[i].F >> p[i].S;
for(int i=0 ; i<m ; i++) cin >> f[i];
for(int i=0 ; i<n ; i++) mn=min(mn,p[i].F);
for(int i=0 ; i<m ; i++) mx=max(mx,f[i]);
if(mx<mn){
cout << "0\n";
return 0;
}
sort(p,p+n,[](pair<int,int> a, pair<int,int> b){
if(a.S==b.S) return a.F<b.F;
return a.S<b.S;
});
sort(f,f+m);
//for(int i=0 ; i<m ; i++) cout << f[i] << (i==m-1 ? '\n' : ' ');
//for(int i=0 ; i<n ; i++) cout << p[i].F << ',' << p[i].S << ' ';
//cout << '\n';
//f.erase(unique(f.begin(),f.end()),f.end());
lb[0]=id[0]=(lower_bound(f,f+m,p[0].F)-f);
for(int i=1 ; i<n ; i++) lb[i]=lower_bound(f,f+m,p[i].F)-f;
//for(int i=0 ; i<n ; i++) cout << id[i] << ' ';
//cout << '\n';
vector<int> v{id[0]};
for(int i=1 ; i<n ; i++){
if(lb[i]==lb[i-1]&&id[i-1]+1<m&&f[id[i-1]+1]>=p[i].F) id[i]=id[i-1]+1;
else id[i]=lb[i];
if(id[i]>v.back()) v.push_back(id[i]);
else *lower_bound(v.begin(),v.end(),id[i])=id[i];
//for(int j:v) cout << j << ' ';
//cout << '\n';
}
cout << v.size() << '\n';
return 0;
}
