#include <bits/stdc++.h>
using namespace std;
typedef long long int ll;
typedef pair<int,int> ii;
const int N = 1e5 + 5;
int n,m;
ii a[N];
int c[N];
vector <int> v;
bool check(int x) {
v.clear();
for (int i = 1 ; i <= x ; i++)
v.push_back(c[i]);
for (int i = 1 ; i <= n ; i++) {
if (v.empty())
return true;
if (a[i].second <= v.back())
v.pop_back();
}
return v.empty();
}
int main() {
ios_base::sync_with_stdio(false);
cin.tie(NULL); cout.tie(NULL);
cin >> n >> m;
for (int i = 1 ; i <= n ; i++)
cin >> a[i].second >> a[i].first;
for (int i = 1 ; i <= m ; i++)
cin >> c[i];
sort(a + 1,a + n + 1);
sort(c + 1,c + m + 1,greater <int>());
int l = 0, r = m;
while(l < r) {
int mid = (l + r + 1) / 2;
if (check(mid))
l = mid;
else
r = mid - 1;
}
cout << l << endl;
}
