#include <bits/stdc++.h>
#define all(x) x.begin(), x.end()
#define sz(x) (int)x.size()
#define x first
#define y second
using namespace std;
using ll = long long;
#define int ll
const int N = 1e6;
int n;
int m;
pair<int, int> a[N]; // { value, size }
int b[N];
bool check(int suff) {
int ptr = 0;
for (int i = m - suff; i < m; ++i) {
while (ptr < n && a[ptr].y > b[i]) {
++ptr;
}
if (ptr == n) {
return false;
} else {
++ptr;
}
}
return true;
}
signed main() {
#ifdef LC
assert(freopen("input.txt", "r", stdin));
#endif
ios::sync_with_stdio(0), cin.tie(0);
cin >> n >> m;
for (int i = 0; i < n; ++i) {
cin >> a[i].y >> a[i].x;
}
sort(a, a + n);
for (int i = 0; i < m; ++i) {
cin >> b[i];
}
sort(b, b + m);
int lef = 0, rig = min(n, m) + 1;
while (rig - lef > 1) {
int mid = (lef + rig) / 2;
if (check(mid)) {
lef = mid;
} else {
rig = mid;
}
}
cout << lef << "\n";
return 0;
}
