#include "bits/stdc++.h"
using namespace std;
/*
#include <ext/pb_ds/assoc_container.hpp>
using namespace __gnu_pbds;
using ordered_set = tree<int, null_type, less<int>, rb_tree_tag, tree_order_statistics_node_update>;
*/
#define all(x) begin(x), end(x)
#define rall(x) rbegin(x), rend(x)
#define sz(x) (int)x.size()
using ll = long long;
const int mod = 1e9+7;
void solve(int tc) {
int n, m;
cin >> n >> m;
priority_queue<pair<int, int>> pq;
while (n--) {
int s, v;
cin >> s >> v;
pq.push({v, s});
}
vector<int> c(m);
for (auto &x : c) cin >> x;
sort(rall(c));
int ans = 0;
for (int x : c) {
while (!pq.empty() and pq.top().second > x)
pq.pop();
if (pq.empty())
break;
pq.pop();
++ans;
}
cout << ans << '\n';
}
signed main() {
ios_base::sync_with_stdio(false); cin.tie(NULL);
int tc = 1;
//cin >> tc;
for (int i = 1; i <= tc; ++i) solve(i);
return 0;
}
