/*
author : PakinDioxide
created : 29/03/2025 01:59
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);
ll n, m;
cin >> n >> m;
pair <ll, ll> a[n];
ll c[m];
for (auto &[y, x] : a) cin >> x >> y;
for (auto &e : c) cin >> e;
sort(a, a+n);
sort(c, c+m);
ll pos[n];
for (int i = 0; i < n; i++) pos[i] = lower_bound(c, c+m, a[i].second) - c;
vector <ll> d;
for (auto &e : pos) {
if (e == m) continue;
int psh = 0;
if (!d.empty() && d.back() < m-1 && d.back() + 1 > e) d.emplace_back(d.back() + 1), psh = 1;
int idx = lower_bound(d.begin(), d.end(), e) - d.begin();
if (idx != d.size()) {
while (d[idx] == e && idx+1 < d.size() && e+1 < m) e++, idx++;
d[idx] = e;
} else if (!psh) d.emplace_back(e);
}
cout << d.size() << '\n';
}
