#include <bits/stdc++.h>
using namespace std;
using ll = long long;
const int maxn = 1e5+5;
int N, M;
int frames[maxn];
int dp[maxn];
struct SegDyn
{
int s, e, m; //represents range [s,e]
SegDyn *l, *r;
int sum; //sum for this interval
SegDyn(int _s, int _e) {
s = _s;
e = _e;
m = (s+e)/2;
l = NULL;
r = NULL;
sum = 0;
}
void prepareL() { if (l == NULL) l = new SegDyn(s,m); }
void prepareR() { if (r == NULL) r = new SegDyn(m+1,e); }
void pull() {
sum = 0;
if (l) sum = max(sum,l->sum);
if (r) sum = max(sum,r->sum);
}
void add(int idx, int x) { //a[idx] = max(a[idx],x)
//cout << s << ' ' << e << '\n';
if (s == e && s == idx) {
//at the node, stop
sum = max(sum,x);
return;
}
if (idx <= m) {
prepareL();
assert(l);
l->add(idx,x);
}
else {
prepareR();
r->add(idx,x);
}
pull(); //updates current node based on the children
}
int getmax(int se, int en) {
if (se <= s && e <= en) return sum;
int res = 0;
if (l && se <= m) res = max(res,l->getmax(se,en));
if (r && en > m) res = max(res,r->getmax(se,en));
return res;
}
};
int main()
{
cin >> N >> M;
vector<pair<int,int>> pictures;
for (int i = 0; i < N; i++) {
int a, b; cin >> a >> b;
pictures.push_back({a,b});
}
//coordinate compress values
/*
sort(pictures.begin(),pictures.end(),[](auto a, auto b) {
return a.second < b.second;
});
map<int,int> comp;
int c = 1;
for (auto& p: pictures) {
if (comp.count(p.second)) p.second = comp[p.second];
else p.second = comp[p.second] = c++;
}
*/
sort(pictures.begin(),pictures.end(),[](auto a, auto b) {
if (a.second != b.second) return a.second < b.second;
return a.first < b.first;
});
for (int i = 1; i <= M; i++) cin >> frames[i];
sort(frames+1,frames+M+1);
SegDyn *root = new SegDyn(0,1000000007);
int ans = 0;
for (int i = N - 1; i >= 0; i--) {
int sz = pictures[i].first;
int val = pictures[i].second;
/*
for (int j = i + 1; j < N; j++) {
if (dp[j] < M && frames[M-dp[j]] >= sz) {
dp[i] = max(dp[i],dp[j]+1);
}
}
*/
if (frames[M] >= sz) {
dp[i] = root->getmax(sz,1000000007) + 1;
}
//cout << i << ": " << dp[i] << '\n';
if (dp[i] < M) root->add(frames[M-dp[i]],dp[i]);
ans = max(ans,dp[i]);
}
cout << ans << '\n';
}
