#include <iostream>
#include <iomanip>
#include <vector>
#include <cmath>
#include <algorithm>
#include <set>
#include <queue>
#include <map>
#include <unordered_map>
#include <stack>
#include <bitset>
#include <string>
#include <cstring>
#include <iterator>
#include <random>
#define ll long long
#define ld long double
#define inf (ll)(2*1e18)
#define sort(a) sort(a.begin(), a.end())
#define reverse(a) reverse(a.begin(), a.end())
#define pb push_back
#define endl "\n"
using namespace std;
void solve(){
ll n, m, i, x, pos;
cin>>n>>m;
vector<pair<ll, ll>> a(n);
vector<ll> b(m);
vector<ll> c;
vector<ll> d;
for(i=0;i<n;++i){
cin>>a[i].second>>a[i].first;
}
for(i=0;i<m;++i){
cin>>b[i];
}
sort(a);
sort(b);
c.pb(0);
d.pb(0);
for(i=0;i<n;++i){
auto it = lower_bound(c.begin(), c.end(), a[i].second);
if(*it == a[i].first) ++it;
if(it == c.end()){
x = d.back();
auto it2 = lower_bound(b.begin()+x, b.end(), a[i].second);
if(it2 == b.end()) continue;
c.pb(a[i].second);
d.pb(it2 - b.begin() + 1);
}else{
pos = it - c.begin();
x = d[pos-1];
auto it2 = lower_bound(b.begin()+x, b.end(), a[i].second);
if(it2 == b.end()) continue;
c[pos] = a[i].second;
d[pos] = it2 - b.begin() + 1;
}
}
cout<<c.size() - 1<<endl;
}
int main() {
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
cout.tie(nullptr);
srand(time(nullptr));
ll t=1;
// cin>>t;
for(;t>0;--t){
solve();
}
return 0;
}
