//STRIKER!
#include <iostream>
#include <vector>
#include <algorithm>
#include <string>
#include <map>
#include <set>
#include <unordered_map>
#include <cmath>
#include <queue>
#include <iomanip>
using namespace std;
#define int int64_t
#define pb push_back
#define speed cin.tie(0);cout.tie(0);ios_base::sync_with_stdio(false);
#define all(a) a.begin(), a.end()
#define sz(a) ((int)a.size())
int n, m;
vector<pair<int, int>> a;
vector<int> sizm;
bool check(int mid) {
multiset<int> st;
int j = 0;
int lst = -1;
for (int i = m - mid; i < m; i++) {
while (j < n and a[j].first <= sizm[i]) {
st.insert(a[j].second);
j++;
}
auto it = st.lower_bound(lst);
if (it == st.end()) {
return 0;
}
lst = *it;
st.erase(it);
}
return 1;
}
void sol() {
cin >> n >> m;
a.resize(n);
sizm.resize(m);
for (int i = 0; i < n; i++) {
cin >> a[i].first >> a[i].second;
}
sort(all(a));
for (int i = 0; i < m; i++) {
cin >> sizm[i];
}
sort(all(sizm));
int l = 0, r = min(m, n), ans = 0;
while (l <= r) {
int mid = (l + r) / 2;
if (check(mid)) {
ans = mid;
l = mid + 1;
}
else {
r = mid - 1;
}
}
cout << ans;
}
int32_t main() {
speed;
int t = 1;
//cin >> t;
while (t--) {
sol();
}
return 0;
}
//freopen("name", "r", stdin);
//freopen("name", "w", stdout);
