#include <bits/stdc++.h>
using namespace std;
const int N = 1e5 + 1;
int n, m, x[N], C[N];
pair<int, int> a[N];
int b[N];
void upd(int i, int x) {
for (; i <= n; i += i & -i) b[i] = max(b[i], x);
}
int get(int i) {
int res = 0;
for (; i; i -= i & -i) res = max(res, b[i]);
return res;
}
int main() {
ios::sync_with_stdio(0);
cin.tie(0);
memset(b, 0xc0, 4 * N);
cin >> n >> m;
for (int i = 1; i <= n; i++) cin >> a[i].second >> a[i].first;
sort(a + 1, a + n + 1);
for (int i = 1; i <= m; i++) cin >> C[i];
sort(C + 1, C + m + 1);
for (int i = 1; i <= n; i++) x[i] = lower_bound(C + 1, C + m + 1, a[i].second) - C - i;
int res = 0;
for (int i = n; i; i--) {
upd(i, x[i]);
int l = i, r = n;
while (l <= r) {
int mid = (l + r) >> 1;
if (m - mid >= get(mid)) l = mid + 1;
else r = mid - 1;
}
res = max(res, r - i + 1);
}
cout << res;
}
