/*
author : PakinDioxide
created : 25/04/2025 20:25
task : JOI19_ho_t2
*/
#include <bits/stdc++.h>
#define ll long long
using namespace std;
int main() {
ios::sync_with_stdio(0), cin.tie(0);
int n, m;
cin >> n >> m;
pair <ll, ll> A[n], K[n];
ll b[m];
for (auto &[x, y] : A) cin >> y >> x;
for (auto &e : b) cin >> e;
sort(b, b+m);
sort(A, A+n);
for (int i = 0; i < n; i++) K[i] = make_pair(A[i].second, i);
sort(K, K+n);
int l = 1, r = min(n, m), ans = 0;
while (l <= r) {
int x = l + (r-l)/2;
vector <pair <int, int>> V;
for (int i = 0; i < x; i++) V.emplace_back(K[i].second, K[i].first);
sort(V.begin(), V.end());
bool ok = 1;
for (int i = m-1; i >= m-x; i--) ok = min(ok, (V[x-(m-1-i)-1].second <= b[i]));
if (ok) l = x+1, ans = x;
else r = x-1;
}
cout << ans << '\n';
}
