#include <bits/stdc++.h>
using namespace std;
const int N = 100005;
int n, m;
int s[N], v[N], c[N];
int ord[N];
int main() {
ios::sync_with_stdio(false);
cin.tie(0);
cin >> n >> m;
for (int i = 1; i <= n; i++) {
cin >> s[i] >> v[i];
}
for (int i = 1; i <= m; i++) {
cin >> c[i];
}
iota(ord + 1, ord + n + 1, 1);
sort(ord + 1, ord + n + 1, [](int &i, int &j) -> bool {
return v[i] > v[j] || (v[i] == v[j] && s[i] > s[j]);
});
sort(c + 1, c + m + 1, greater<int>());
int ans = 0;
for (int i = 1, j = 1; i <= m; i++) {
while (j < n && s[ord[j]] > c[i]) {
++j;
}
if (j <= n && s[ord[j]] <= c[i]) {
++ans;
++j;
}
}
cout << ans;
return 0;
}
