#include <bits/stdc++.h>
using namespace std;
int main() {
ios::sync_with_stdio(false);
cin.tie(nullptr);
int n, m;
cin >> n >> m;
vector<pair<int, int>> a(n); //value, size
vector<int> c(m);
for (int i = 0; i < n; ++i) {
cin >> a[i].second >> a[i].first;
}
for (int i = 0; i < m; ++i) {
cin >> c[i];
}
sort(a.begin(), a.end(), greater());
sort(c.begin(), c.end(), greater());
int pnt = 0;
int ans = 0;
for (int i = 0; i < m; ++i) {
while (pnt < n && a[pnt].second > c[i]) {
pnt += 1;
}
if (pnt == n) {
break;
}
ans += 1;
pnt += 1;
}
cout << ans;
return 0;
}
