#include <bits/stdc++.h>
#define pii pair <long long, long long>
#define fi first
#define se second
using namespace std;
using ll = long long;
const ll N = 5e5, inf = 1e18;
int n, m;
pii a[N];
ll b[N];
multiset <pii, greater <pii> > s; // sort theo max
signed main() {
cin >> n >> m;
for (int i = 1; i <= n; i++) {
cin >> a[i].fi >> a[i].se; // fi la size, se la value
s.insert({a[i].se, a[i].fi});
}
for (int i = 1; i <= m; i++) {
cin >> b[i];
}
sort(b + 1, b + m + 1, greater<ll>());
ll ans = 0;
for (int i = 1; i <= m; i++) {
while(s.size() && s.begin()->se > b[i]) s.erase(s.begin());
if (!s.size()) break;
ans++;
s.erase(s.begin());
}
cout << ans;
return 0;
}
