#include <bits/stdc++.h>
using namespace std;
template<class A, class B>
ostream& operator<<(ostream& o, const pair<A, B>& p) {
return o << '(' << p.first << ", " << p.second << ')';
}
template<class T>
auto operator<<(ostream& o, const T& x) -> decltype(x.end(), o) {
o << '{';
bool first = true;
for (const auto& e : x) {
if (!first) {
o << ", ";
}
o << e;
first = false;
}
return o << '}';
}
#define DEBUG
#ifdef DEBUG
#define fastio()
#define debug(x...) cerr << "[" #x "]: ", [](auto... $) {((cerr << $ << "; "), ...); }(x), cerr << '\n'
#define check(x) if (!(x)) { cerr << "Check failed: " << #x << " in line " << __LINE__ << endl; exit(1); }
#else
#define fastio() ios_base::sync_with_stdio(0); cin.tie(0);
#define debug(...)
#define check(x)
#endif
typedef long long ll;
#define pi pair<int, int>
#define pl pair<ll, ll>
#define st first
#define nd second
#define vi vector<int>
#define vll vector<ll>
#define pb push_back
#define all(x) (x).begin(), (x).end()
#define sz(x) (int)(x).size()
void solve() {
int n, m;
cin >> n >> m;
vector<pi>tab;
for(int i = 1; i <= n; i++) {
int a, b;
cin >> a >> b;
tab.pb({a, b});
}
sort(all(tab));
vi tab2;
for(int i = 1; i <= m; i++) {
int x;
cin >> x;
tab2.pb(x);
}
sort(all(tab2));
int l = 0;
int r = m;
while(l < r) {
int mid = (l + r + 1) / 2;
int pop = 0;
int j = 0;
multiset<int>akt;
int ans = 0;
for(int i = m - mid; i < m; i++) {
while(j < sz(tab) && tab[j].st <= tab2[i]) {
if(tab[j].nd >= pop) {
akt.insert(tab[j].nd);
}
j++;
}
if(akt.size()) {
ans++;
auto it = akt.find(*akt.begin());
pop = *akt.begin();
akt.erase(it);
}
}
if(ans == mid) {
l = mid;
}
else {
r = mid - 1;
}
}
cout << l << '\n';
}
int main() {
fastio();
int t;
//cin >> t;
t = 1;
while(t--) {
solve();
}
}
