#include <iostream>
#include <vector>
#include <cmath>
#include <algorithm>
#include <deque>
#include <map>
#include <set>
#include <complex>
#include <string>
#include <unordered_map>
#include <unordered_set>
#include <random>
#define ft first
#define sc second
#define pb push_back
#define len(v) (int)v.size()
#define int ll
using namespace std;
typedef long long ll;
signed main() {
#ifdef PC
freopen("in.txt", "r", stdin);
freopen("out.txt", "w", stdout);
#endif
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
int n, m;
cin >> n >> m;
vector<pair<int, int>> have;
vector<int> fr;
for (int i = 0; i < n; i++) {
int v, sz;
cin >> sz >> v;
have.pb({v, sz});
}
for (int i = 0; i < m; i++) {
int sz;
cin >> sz;
fr.pb(sz);
}
sort(have.begin(), have.end());
reverse(have.begin(), have.end());
sort(fr.begin(), fr.end());
int ans = 0;
for (int i = 0; i < n; i++) {
if(len(fr) == 0)
continue;
if(have[i].sc <= fr.back()) {
ans++;
fr.pop_back();
}
}
cout << ans;
return 0;
}
