#include <bits/stdc++.h>
using namespace std;
int main() {
cin.tie(0)->sync_with_stdio(0);
int n, m;
cin >> n >> m;
vector<pair<int,int>> a(n);
for (auto &i : a) {
cin >> i.second >> i.first;
}
vector<int> b(m);
for (auto &i : b) {
cin >> i;
}
sort(a.begin(), a.end(), greater<pair<int,int>>());
sort(b.begin(), b.end(), greater<int>());
int ans = 0;
for (int i = 0, j = 0; i < (int) b.size(); i++) {
while (j < (int) a.size() && a[j].second > b[i]) j++;
if (j < (int) a.size() && a[j].second <= b[i]) {
ans++;
j++;
}
}
cout << ans << '\n';
}
