#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
mt19937 rnd(chrono::high_resolution_clock::now().time_since_epoch().count());
int main() {
ios::sync_with_stdio(0);
cin.tie(0);
int n, m;
cin >> n >> m;
vector <pair <int, int> > p;
for (int i = 0; i < n; i++) {
int x, y;
cin >> x >> y;
p.push_back({y, x});
}
sort(p.begin(), p.end());
vector <int> c;
for (int i = 0; i < m; i++) {
int x;
cin >> x;
c.push_back(x);
}
sort(c.begin(), c.end());
int ans = 0;
int ptr = m - 1;
for (int i = n - 1; i >= 0; i--) {
if (ptr >= 0 && c[ptr] >= p[i].second) {
ptr--;
ans++;
}
}
cout << ans << endl;
return 0;
}
