#include "bits/stdc++.h"
using namespace std;
#define vec vector
#define int long long
#define all(x) (x).begin(), (x).end()
const int mod = 998244353;
const int inf = LLONG_MAX;
using pii = pair<int, int>;
signed main() {
int n, m; cin >> n >> m;
vec<pii> pictures(n);
for(auto &[s, v]: pictures) cin >> s >> v;
sort(pictures.begin(), pictures.end(), [](const pii &a, const pii &b) {
return a.second < b.second;
});
vec<int> frames(m);
for(int &x: frames) cin >> x;
sort(all(frames));
int ans = 0;
vec<int> subset; subset.reserve(n);
for (int mask = 0; mask < (1 << n); ++mask) {
subset.clear();
for (int i = 0; i < n; ++i) {
if (mask & (1 << i)) {
subset.push_back(pictures[i].first);
}
}
int i = 0, j = 0;
while (j < m && i < (int)subset.size()) {
if (frames[j] >= subset[i]) {
i++;
j++;
} else j++;
}
if (i == (int)subset.size()) ans = max(ans, i);
}
cout << ans << endl;
}
