#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define int ll
using P = pair<int, int>;
#define all(x) x.begin(), x.end()
#define rep(i, l, n) for (int i = l; i < (n); ++i)
#define sz(x) (int)x.size()
const char nl = '\n';
const int mod = 998244353;
void solve() {
int n, m; cin >> n >> m;
vector<P> a(n);
for (auto &i: a)cin >> i.second >> i.first;
vector<int> b(m);
for (auto &i: b)cin >> i;
sort(all(a));
sort(all(b));
vector<int> dp(m), dp2(m);
rep(i, 0, n) {
int lb = lower_bound(all(b), a[i].second) - b.begin();
if (lb < sz(b)) {
int mx = 0;
rep(j, 0, lb)
mx = max(mx, dp[j]);
rep(j, lb, m) {
int b = max(mx, dp[j]);
dp[j] = max(dp[j], mx+1);
mx = b;
}
//dp[lb] = max(dp[lb], mx+1);
}
}
cout << *max_element(all(dp));
}
int32_t main() {
ios_base::sync_with_stdio(0);
cin.tie(0);
solve();
return 0;
}
