#include <iostream>
#include <algorithm>
#include <vector>
using namespace std;
int n, m, x;
vector <pair <int, int>> v;
vector <int> f;
int main() {
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cin >> n >> m;
v.resize(n);
f.resize(m);
for (auto& p : v) cin >> p.second >> p.first;
for (int& i : f) cin >> i;
sort(v.begin(), v.end());
sort(f.begin(), f.end());
reverse(v.begin(), v.end());
for (auto p : v) {
int l = f.end() - lower_bound(f.begin(), f.end(), p.second);
if (l > x) x++;
}
cout << x;
}
