#include <bits/stdc++.h>
using namespace std;
#define int long long
typedef pair<int, int> pii;
#define ff first
#define ss second
#define MP make_pair
const int inf = 1e18 + 10;
const int mxn = 2e5 + 10;
int s[mxn], v[mxn], c[mxn];
int val[mxn];
int n, m, k = 1;
int32_t main() {
cin >> n >> m;
map<int, int> mp;
for(int i = 1; i <= n; i++) {
cin >> s[i] >> v[i];
mp[s[i]];
}
for(int i = 1; i <= m; i++) {
cin >> c[i];
mp[c[i]];
}
priority_queue<pii> pq;
multiset<pii> ms;
for(int i = 1; i <= n; i++) {
pq.push(MP(s[i], v[i]));
ms.insert(MP(v[i], s[i]));
}
for(int i = 1; i <= m; i++) {
pq.push(MP(c[i], inf));
}
int ans = 0;
while(pq.size()) {
if(ms.size() == 0) break;
int SIZE = pq.top().ff;
int val = pq.top().ss;
pq.pop();
if(val < inf) {
auto it = ms.find(MP(val, SIZE));
if(it == ms.end()) continue;
ms.erase(it);
}
else {
auto it = ms.end();
it--;
ms.erase(it);
ans++;
}
}
cout << ans << endl;
return 0;
}
