#include <bits/stdc++.h>
using namespace std;
int main() {
ios_base::sync_with_stdio(0); cin.tie(0);
int n, m;
cin >> n >> m;
pair<int, int> a[n + 1];
for(int i = 1; i <= n; ++i)
cin >> a[i].first >> a[i].second;
sort(a + 1, a + n + 1);
int b[m + 1];
for(int i = 1; i <= m; ++i)
cin >> b[i];
sort(b + 1, b + m + 1);
// coba minimum value yg bs masuk ke frame
int l = 0, r = m, res = 0;
while(l <= r) {
int mid = (l + r) / 2;
int idx = 1;
multiset<int> s;
int pr = 0;
bool ans = 1;
//cout << "MID " << mid << endl;
for(int i = m - mid + 1; i <= m; ++i) {
while(idx <= n && a[idx].first <= b[i]) {
s.insert(a[idx].second);
//cout << "DEBUG " << i << " " << a[idx].second << endl;
++idx;
}
// ambil 1
//cout << pr << endl;
if(s.lower_bound(pr) == s.end()) {
ans = 0;
break;
}
else {
pr = *s.lower_bound(pr);
s.erase(s.lower_bound(pr));
}
}
if(ans)
l = mid + 1, res = mid;
else
r = mid - 1;
}
cout << res << endl;
return 0;
}
