#include <bits/stdc++.h>
#define f first
#define s second
using namespace std;
struct FenwickTree {
int N;
vector<int> fw, a;
void update(int x, int v) {
int u = a[x];
while (x <= N) fw[x] += v - u, x += x & -x;
a[x] = v;
}
int query(int x) {
int res = 0;
while (x > 0) res += fw[x], x -= x & -x;
return res;
}
} T;
int main() {
ios_base::sync_with_stdio(0); cin.tie(0);
int n, m;
cin >> n >> m;
vector<pair<int, int>> a(n+1), b(m+1);
for (int i = 1; i <= n; i++) cin >> a[i].s >> a[i].f;
for (int i = 1; i <= m; i++) cin >> b[i].f, b[i].s = INT_MAX;
sort(a.begin() + 1, a.end());
sort(b.begin() + 1, b.end());
T.N = m;
T.fw.assign(m+1, 0);
T.a.assign(m+1, 0);
int ans = 0;
for (int i = 1; i <= n; i++) {
if (b.back().f < a[i].s || b.back().f == a[i].s && b.back().s <= a[i].s) continue;
int id = upper_bound(b.begin() + 1, b.end(), make_pair(a[i].s, a[i].s)) - b.begin();
int t = T.query(id-1) + 1;
if (t > ans) T.update(id, 1), ans = t;
b[id] = {a[i].s, a[i].s};
}
cout << ans;
}
