//Dedicated to my love, ivaziva
#include <bits/stdc++.h>
using namespace std;
using pii = pair<int, int>;
using ll = int64_t;
#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
#define dbg(x) cerr << #x << ": " << x << '\n';
int32_t main() {
ios::sync_with_stdio(false);
cin.tie(nullptr);
cout.tie(nullptr);
cerr.tie(nullptr);
int n, m;
cin >> n >> m;
vector<pii> a(n);
for (int i = 0; i < n; i++) {
cin >> a[i].first >> a[i].second;
swap(a[i].first, a[i].second);
}
sort(all(a));
vector<int> b(m);
for (int i = 0; i < m; i++) {
cin >> b[i];
}
sort(all(b));
int ans = 0, pt1 = n - 1, pt2 = m - 1;
// vector<pii> dp(n);
while (pt1 >= 0 && pt2 >= 0) {
if (b[pt2] >= a[pt1].second) {
pt2--;
ans++;
}
pt1--;
}
cout << ans << '\n';
}
