#include <bits/stdc++.h>
using namespace std;
const int MAX = 1e5 + 10;
int N,M;
vector<pair<int,int>> pics(MAX);
vector<int> C(MAX);
bool check(int k) {
int j = 0;
for (int i = 0; i < k; i++) {
while (j < N && pics[j].first > C[M-k+i]) j++;
if (j == N) return false;
j++;
}
return true;
}
int main() {
cin >> N >> M;
for (int i = 0; i < N; i++) cin >> pics[i].first >> pics[i].second;
for (int i = 0; i < M; i++) cin >> C[i];
sort(pics.begin(),pics.begin()+N,[](pair<int,int> p1, pair<int,int> p2) {return p1.second < p2.second;});
sort(C.begin(),C.begin()+M);
int k = 0; int high = N+1;
for (int b = high/2; b > 0; b /= 2) {
while (k + b < high && check(k+b)) k += b;
}
cout << k << "\n";
return 0;
}
