#include <iostream>
#include <vector>
#include <algorithm>
#define ll long long
using namespace std;
struct pict {
ll s;
ll v;
pict(){}
pict(ll s, ll v) : s(s), v(v) {}
};
bool cmp(pict& A, pict& B) {
if (A.v != B.v)
return A.v < B.v;
return A.s < B.s;
}
int n, m;
bool check(vector<pict>& arr, vector<ll>& f, int x) {
int ind = m - x;
int pt = 0;
while (ind < m && pt < n) {
if (arr[pt].s <= f[ind]) {
ind++;
pt++;
continue;
}
pt++;
}
return (ind == m);
}
int main() {
cin >> n >> m;
vector<pict> arr(n);
for (int i = 0; i < n; i++) {
ll s, v;
cin >> s >> v;
arr[i] = { s, v };
}
sort(arr.begin(), arr.end(), cmp);
vector<ll> f(m);
for (int i = 0; i < m; i++)
cin >> f[i];
sort(f.begin(), f.end());
int L = -1;
int R = min(n, m) + 1;
while (R - L > 1) {
int M = (L + R) / 2;
if (check(arr, f, M))
L = M;
else
R = M;
}
cout << L << endl;
}
