#include <bits/stdc++.h>
using namespace std;
#define f first
#define s second
int N, M;
vector<pair<int, int>> pictures;
vector<int> frames;
int main() {
ios::sync_with_stdio(false);
cin.tie(nullptr);
cin >> N >> M;
pictures.resize(N);
frames.resize(M);
for (int i = 0; i < N; i++) {
cin >> pictures[i].s >> pictures[i].f;
}
for (int i = 0; i < M; i++) {
cin >> frames[i];
}
sort(pictures.begin(), pictures.end());
sort(frames.begin(), frames.end());
int finalAns = 0;
for (int i = 0; i < N; i++) {
if ((i == N-1) || (pictures[i].s > pictures[i+1].s)) {
int j = i;
int k = M-1;
int localAns = 0;
while ((j >= 0) && (k >= 0)) {
bool flag = false;
while (pictures[j].s > frames[k]) {
j--;
if (j < 0) {
flag = true;
break;
}
}
if (flag) break;
localAns++;
j--;
k--;
}
finalAns = max(localAns, finalAns);
}
}
cout << finalAns << "\n";
}
