#include<bits/stdc++.h>
#define IOS ios_base::sync_with_stdio(false);cin.tie();cout.tie();
#define all(x) x.begin(), x.end()
#define int long long
#define pq priority_queue
#define eb emplace_back
#define lb lower_bound
#define ub upper_bound
#define pb push_back
#define pp pop_back
#define F first
#define S second
using namespace std;
void solve () {
int n, m; cin >> n >> m;
vector<pair<int, int>> v(n);
vector<int> c(m);
for (auto &i: v) cin >> i.S >> i.F;
for (int &i: c) cin >> i;
sort(v.rbegin(), v.rend());
sort(c.rbegin(), c.rend());
c.pb(-1);
int j = 0;
for (int i = 0; i < n; i++)
if (v[i].F <= c[j]) j++;
cout << j << '\n';
}
signed main() {IOS solve(); return 0;}
