#include <bits/stdc++.h>
#define int long long
using namespace std;
typedef pair<int, int> pii;
inline void solve()
{
int n, m;
cin >> n >> m;
vector<pii> v(n);
for (pii &i : v)
cin >> i.second >> i.first;
vector<int> f(m);
for (auto &i : f)
cin >> i;
sort(v.begin(), v.end()), sort(f.begin(), f.end());
reverse(v.begin(), v.end()), reverse(f.begin(), f.end());
// cout << '\n';
// for (auto i : v)
// cout << i.first << ' ' << i.second << '\n';
// for (int i : f)
// cout << i << ' ';
// cout << '\n';
int mx = 0, cur = 0;
for (pii i : v)
{
while (cur >= 0 && f[cur] < i.second)
--cur;
mx = max(mx, ++cur);
}
cout << min(mx, m) << '\n';
}
signed main()
{
ios::sync_with_stdio(0), cin.tie(0), cout.tie(0);
solve();
return 0;
}
