#include <bits/stdc++.h>

using ll = long long;
using namespace std;

signed main() {
#ifdef LOCAL
    freopen("input.txt", "r", stdin);
    freopen("output.txt", "w", stdout);
#else
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
#endif
    
    int n, m;
    cin >> n >> m;

    vector<pair<int, int>> a(n);
    for (auto &[s, v] : a) {
        cin >> s >> v;
    }

    sort(a.begin(), a.end(), [&](auto A, auto B) {
        return A.second < B.second || (A.second == B.second && A.first < B.first);
    });

    vector<int> b(n);
    for (int i = 0; i < n; i++) {
        b[i] = a[i].first;
    }

    vector<int> c(m);
    for (int i = 0; i < m; i++) {
        cin >> c[i];
    }

    sort(c.begin(), c.end());

    int j = n - 1;
    int cnt = 0;

    for (int i = m - 1; i >= 0; i--) {
        while (j >= 0 && b[j] > c[i]) {
            j--;
        }

        if (j >= 0 && b[j] <= c[i]) {
            cnt += 1;
            j--;
        }
    }

    cout << cnt << '\n';
    return 0;
}