#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace std;
using namespace __gnu_pbds;
template<typename T> using ordered_set = tree<T, null_type, less_equal<T>, rb_tree_tag, tree_order_statistics_node_update>;
int main() {
ios::sync_with_stdio(false);
cin.tie(nullptr);
int n,m; cin >> n >> m;
pair<int,int> paint[n];
int frame[m];
for (auto& [v, s] : paint) cin >> s >> v;
for (int& f : frame) cin >> f;
map<int, vector<int*>> comp;
for (int i = 0; i < n; i++) {
auto& [v, s] = paint[i];
comp[v].push_back(&v);
comp[s].push_back(&s);
}
for (int i = 0; i < m; i++) {
comp[frame[i]].push_back(&frame[i]);
}
int z = 0;
for (auto [_, list] : comp) {
for (auto i : list) {
*i = z;
}
z++;
}
sort(paint, paint + n, greater<>());
sort(frame, frame + m, greater<>());
int dp[n], ans = 0;
for (int i = 0; i < n; i++) {
dp[i] = 0;
auto [vi, si] = paint[i];
for (int j = 0; j < i; j++) {
auto [vj, sj] = paint[j];
if (vj >= vi) {
dp[i] = max(dp[i], dp[j] + 1);
}
}
dp[i] = min(dp[i], m-1);
while (dp[i] >= 0 && si > frame[dp[i]])
dp[i]--;
ans = max(ans, 1 + dp[i]);
}
cout << ans;
}
