#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define pb push_back
#define fi first
#define se second
int wie;
int tree_size(int n) {
int wynik = 1;
while (wynik < n) wynik *= 2;
return wynik * 2;
}
void update(vector<int>& tree, int i, int x) {
i += wie / 2;
tree[i] = x;
while (i > 1) {
i /= 2;
tree[i] = max(tree[2 * i], tree[2 * i + 1]);
}
}
int query(vector<int>& tree, int l, int r) {
if (l > r) return 0;
l += wie / 2;
r += wie / 2;
int res = 0;
while (l <= r) {
if (l % 2 == 1) res = max(res, tree[l++]);
if (r % 2 == 0) res = max(res, tree[r--]);
l /= 2;
r /= 2;
}
return res;
}
void ctree(vector<int>& tree) {
cout << "drzewo" << endl;
for (int poz = 0; (1 << (poz + 1)) <= wie; poz++) {
for (int j = (1 << poz); j < (1 << (poz + 1)); j++) {
cout << tree[j] << " ";
}
cout << endl;
}
cout << endl;
}
int main() {
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
int n, m, x;
cin >> n >> m;
wie = tree_size(m);
vector<int> dp(wie, 0);
vector<pair<int, int>> obr(n);
multiset<int> roz;
for (int i = 0; i < n; i++) cin >> obr[i].se >> obr[i].fi;
for (int i = 0; i < m; i++) {
cin >> x;
roz.insert(x);
}
auto it = roz.begin();
unordered_map<int, deque<int>> mapa;
for (int i = 0; i < m; i++) {
mapa[*it].push_front(i);
it++;
}
sort(obr.begin(), obr.end());
for (pair<int, int> p : obr) {
auto it = roz.lower_bound(p.se);
if (it == roz.end()) continue;
update(dp, mapa[*it].back(), query(dp, 0, mapa[*it].back() - 1) + 1);
mapa[*it].pop_back();
roz.erase(it);
}
cout << query(dp, 0, m - 1);
}
