#include <bits/stdc++.h>
using namespace std;
#ifdef LOCAL
#include "debug.h"
#else
#define debug(...) 42
#endif
int main() {
ios::sync_with_stdio(false); cin.tie(nullptr);
int N, M; cin >> N >> M;
vector<array<int, 2>> A(N);
for (int i = 0; i < N; ++i) {
cin >> A[i][1] >> A[i][0];
}
sort(A.begin(), A.end());
vector<int> C(M);
for (int i = 0; i < M; ++i) {
cin >> C[i];
}
sort(C.rbegin(), C.rend());
int cnt = 0;
for (int x : C) {
while (A.size() && A.back()[1] > x) {
A.pop_back();
}
if (A.size()) {
A.pop_back();
++cnt;
}
}
cout << cnt;
return 0;
}
