#include <algorithm>
#include <iostream>
using namespace std;
const int N = 100000;
const int M = 100000;
const int INF = 0x3f3f3f3f;
int aa[N], bb[N], iia[N], iib[N], cc[M];
int pq[N], iq[N + 1], pq_cnt;
bool lt(int i, int j) {
return bb[i] > bb[j];
}
int p2(int p) {
return (p <<= 1) > pq_cnt ? 0 : p ^ (p < pq_cnt && lt(iq[p + 1], iq[p]));
}
void pq_up(int i) {
int j, p, q;
for (p = pq[i]; (q = p >> 1) && lt(i, j = iq[q]); p = q)
iq[pq[j] = p] = j;
iq[pq[i] = p] = i;
}
void pq_dn(int i) {
int j, p, q;
for (p = pq[i]; (q = p2(p)) && lt(j = iq[q], i); p = q)
iq[pq[j] = p] = j;
iq[pq[i] = p] = i;
}
void pq_add_last(int i) {
iq[pq[i] = ++pq_cnt] = i;
}
void pq_remove(int i) {
if (pq[i]) {
int j = iq[pq_cnt--];
if (i != j)
pq[j] = pq[i], pq_up(j), pq_dn(j);
pq[i] = 0;
}
}
int pq_remove_first() {
int i = iq[1], j = iq[pq_cnt--];
if (i != j)
pq[j] = 1, pq_dn(j);
pq[i] = 0;
return i;
}
int main() {
ios_base::sync_with_stdio(false), cin.tie(NULL);
int n, m; cin >> n >> m;
for (int i = 0; i < n; i++)
cin >> aa[i] >> bb[i], iia[i] = iib[i] = i;
for (int j = 0; j < m; j++)
cin >> cc[j];
sort(iia, iia + n, [] (int i, int j) { return aa[i] > aa[j]; });
sort(iib, iib + n, [] (int i, int j) { return bb[i] > bb[j]; });
sort(cc, cc + m, greater<>());
for (int i = 0; i < n; i++)
pq_add_last(i);
for (int p = pq_cnt >> 1; p; p--)
pq_dn(p);
for (int ha = 0, hb = 0, b = INF, j = 0; j < m; j++) {
int c = cc[j];
for (int i; ha < n && aa[i = iia[ha]] > c; ha++)
pq_remove(i);
for (int i; hb < n && bb[i = iib[hb]] > b; hb++)
pq_remove(i);
if (!pq_cnt) {
cout << j << '\n';
return 0;
}
b = bb[pq_remove_first()];
}
cout << m << '\n';
return 0;
}
