#include "bits/stdc++.h"
using namespace std;
#define for_(i, s, e) for (int i = s; i < (int) e; i++)
#define for__(i, s, e) for (ll i = s; i < e; i++)
typedef long long ll;
typedef vector<int> vi;
typedef array<int, 2> ii;
#define endl '\n'
int main() {
#ifdef mlocal
freopen("test.in", "r", stdin);
#endif
ios_base::sync_with_stdio(false);
cin.tie(0);
int n, m; cin >> n >> m;
ii pic[n];
int sz[m];
for_(i, 0, n) cin >> pic[i][1] >> pic[i][0];
sort(pic, pic+n, greater<>());
for_(i, 0, m) cin >> sz[i];
sort(sz, sz+m, greater<>());
int ans = 0, pt = 0;
for_(i, 0, m) {
while (pt < n and sz[i] < pic[pt][1]) pt++;
if (pt < n) {
pt++;
ans++;
}
}
cout << ans << endl;
return 0;
}
