#include <bits/stdc++.h>
#include <experimental/random>
#include <random>
//#include <ext/pb_ds/assoc_container.hpp>
//using namespace __gnu_pbds;
using namespace std;
using ld = long double;
using ll = long long;
const ll INF = 3e18, MOD = 1e9 + 7;
void solve();
signed main() {
#ifdef LOCAL
freopen("input.txt", "r", stdin);
freopen("output.txt", "w", stdout);
#endif
ios::sync_with_stdio(false);
cin.tie(0);
int q = 1;
//cin >> q;
while (q--) {
solve();
}
}
struct seg_tree {
vector<ll> tree;
void change(ll v, ll vl, ll vr, ll pos, ll x) {
if (vr - vl == 1) {
tree[v] = max(tree[v], x);
return;
}
ll m = (vl + vr) / 2;
if (pos < m) {
change(2 * v, vl, m, pos, x);
} else {
change(2 * v + 1, m, vr, pos, x);
}
tree[v] = max(tree[2 * v], tree[2 * v + 1]);
}
ll get(ll v, ll vl, ll vr, ll l, ll r) {
if (vl >= r || vr <= l) {
return 0;
}
if (vl >= l && vr <= r) {
return tree[v];
}
ll m = (vl + vr) / 2;
return max(get(2 * v, vl, m, l, r), get(2 * v + 1, m, vr, l, r));
}
};
void solve() {
ll n, m; cin >> n >> m;
vector<pair<ll, ll>> a(n);
vector<ll> cord;
for (int i = 0; i < n; i++) {
cin >> a[i].first >> a[i].second;
cord.push_back(a[i].second);
}
sort(a.rbegin(), a.rend());
vector<ll> c(m);
for (int i = 0; i < m; i++) {
cin >> c[i];
}
sort(c.rbegin(), c.rend());
vector<ll> cnt(n);
ll id = 0;
for (int i = 0; i < n; i++) {
while (id < m && c[id] >= a[i].first) {
id++;
}
cnt[i] = id;
}
sort(cord.begin(), cord.end());
cord.resize(unique(cord.begin(), cord.end()) - cord.begin());
ll len = (int)cord.size();
seg_tree t;
t.tree.resize(4 * len);
ll ans = 0;
for (int i = 0; i < n; i++) {
if (cnt[i] == 0) continue;
ll idx = lower_bound(cord.begin(), cord.end(), a[i].second) - cord.begin();
ll cur = min(cnt[i], t.get(1, 0, len, idx, len) + 1);
ans = max(ans, cur);
t.change(1, 0, len, idx, cur);
}
cout << ans;
}
