#include <bits/stdc++.h>
using namespace std;
#ifdef LOCAL
#include "C:\GCC\debug.h"
#else
#define debug(...) void(42)
#endif
int main() {
ios::sync_with_stdio(false);
cin.tie(0);
int n, m;
cin >> n >> m;
vector<array<int, 2>> a(n);
for (int i = 0; i < n; i++) {
cin >> a[i][1] >> a[i][0];
}
sort(a.begin(), a.end());
vector<int> c(m);
for (int i = 0; i < m; i++) {
cin >> c[i];
}
sort(c.begin(), c.end());
vector<int> sizes(n);
for (int i = 0; i < n; i++) {
sizes[i] = a[i][1];
}
auto Check = [&](int p) {
int l = m - p, r = m - 1;
vector<int> cur;
for (int i = l; i <= r; i++) {
cur.push_back(c[i]);
}
reverse(cur.begin(), cur.end());
int ptr = 0;
while (ptr < n && (int) cur.size() > 0) {
if (sizes[ptr] <= cur.back()) {
cur.pop_back();
}
ptr++;
}
return (cur.empty());
};
int low = 0, high = m;
while (low <= high) {
int mid = low + (high - low) / 2;
if (Check(mid)) {
low = mid + 1;
} else {
high = mid - 1;
}
}
--low;
cout << low << '\n';
return 0;
}
