//#pragma GCC optimize("O3")
//#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,tune=native")
//#pragma GCC optimize ("unroll-loops")
#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ld = long double;
int main() {
ios::sync_with_stdio(false);
cin.tie(nullptr);
cout.tie(nullptr);
int n, m;
cin >> n >> m;
vector<pair<int, int>> a(n);
for (int i = 0; i < n; i++) {
cin >> a[i].first >> a[i].second;
}
sort(a.begin(), a.end());
vector<int> b(m);
for (int i = 0; i < m; i++) {
cin >> b[i];
}
sort(b.begin(), b.end());
int l = 0, r = min(n, m) + 1;
while (l + 1 < r) {
int mid = (l + r) / 2;
int prev = 0;
multiset<int> s;
int it = 0;
bool f = true;
for (int i = m - mid; i < m; i++) {
while (it < n && a[it].first <= b[i]) {
s.insert(a[it++].second);
}
auto kek = s.lower_bound(prev);
if (kek != s.end()) {
prev = *kek;
s.erase(kek);
} else {
f = false;
break;
}
}
if (f) {
l = mid;
} else {
r = mid;
}
}
cout << l;
return 0;
}
