#include <bits/stdc++.h>
using namespace std;
using ll = long long;
ll INF = 1e18;
ll MOD = 1e9 + 7;
vector<ll> z;
vector<ll> tree;
ll sum(ll v, ll vl, ll vr, ll l, ll r) {
if (l >= vr || vl >= r) {
return 0;
}
if (l <= vl && r >= vr) {
return tree[v];
}
ll mid = (vr + vl) / 2;
return max(sum(v * 2, vl, mid, l, r), sum(v * 2 + 1, mid, vr, l, r));
}
void change(ll v, ll vl, ll vr, ll ind, ll x) {
if (vr - vl == 1) {
tree[v] = x;
return;
}
ll mid = (vr + vl) / 2;
if (ind < mid) {
change(v * 2, vl, mid, ind, x);
} else {
change(v * 2 + 1, mid, vr, ind, x);
}
tree[v] = max(tree[v * 2], tree[v * 2 + 1]);
}
int main() {
ios::sync_with_stdio(false);
cin.tie(nullptr);
cout.tie(nullptr);
ll n, m;
cin >> n >> m;
vector<pair<ll, ll>> s(n);
z.assign(n, 0);
vector<ll> c(m);
map<ll, ll> mp;
for (ll i = 0; i < n; i++) {
cin >> s[i].first >> s[i].second;
mp[s[i].second] = 0;
}
ll d = 0;
for (auto to: mp) {
mp[to.first] = d;
d++;
}
for (ll i = 0; i < s.size(); i++) {
s[i].second = mp[s[i].second];
}
std::sort(s.begin(), s.end());
for (ll i = 0; i < s.size(); i++) {
z[i] = s[i].second;
}
for (ll i = 0; i < m; i++) {
cin >> c[i];
}
sort(c.rbegin(), c.rend());
tree.assign((d + 2) * 4, 0);
for (ll i = n - 1; i >= 0; i--) {
ll k = sum(1, 0, d + 1, z[i], d + 1);
if (c[k] >= s[i].first) {
change(1, 0, d + 1, z[i], k + 1);
}
}
cout << tree[1] << endl;
}
