#include <bits/stdc++.h>
using namespace std;
using ll = long long;
const int MAXN = (int)(2e5)+5;
int dp[MAXN];
int main() {
int N, M;
cin >> N >> M;
vector<pair<int, int>> F(N);
vector<int> C(M);
for (int i = 0; i < N; i++) {
int f, s;
cin >> f >> s;
F[i] = {s, f};
}
for (int i = 0; i < M; i++) {
cin >> C[i];
}
sort(F.rbegin(), F.rend());
sort(C.rbegin(), C.rend());
dp[0] = (F[0].second <= C[0]);
int curMax = dp[0];
for (int i = 1; i < N; i++) {
int low = 0;
int high = M-1;
while (low < high) {
int mid = (low + high+1)/2;
if (C[mid] >= F[i].second) {
low = mid;
}
else {
high = mid-1;
}
}
dp[i] = min(curMax+1, low+1);
if (C[0] < F[i].second) {
dp[i] = 0;
}
curMax = max(dp[i], curMax);
}
cout << curMax << '\n';
}
