// #pragma optimize ("g",on)
// #pragma GCC optimize ("inline")
// #pragma GCC optimize ("Ofast")
// #pragma GCC optimize ("unroll-loops")
// #pragma GCC optimize ("03")
#include <bits/stdc++.h>
#define pb push_back
#define SS ios_base::sync_with_stdio(0);cin.tie(nullptr);cout.tie(nullptr);
#define int long long
#define all(v) v.begin(),v.end()
using namespace std;
mt19937 rnd(chrono::steady_clock::now().time_since_epoch().count());
const int N = 4e5 + 1, inf = 1e9, mod = 998244353;
pair<int, int> t[4 * N];
pair<int, int> f(pair<int, int> a, pair<int, int> b){
if(a.first > b.first) return a;
if(a.first < b.first) return b;
if(a.second <= b.second) return a;
else return b;
}
void upd(int v, int tl, int tr, int pos, int x, int y){
if(tl == tr){
t[v] = f(t[v], make_pair(x, y));
return;
}
int mid = (tl + tr) / 2;
if(mid >= pos) upd(v * 2, tl, mid, pos, x, y);
else upd(v * 2 + 1, mid + 1, tr, pos, x, y);
t[v] = f(t[v * 2], t[v * 2 + 1]);
}
pair<int, int> get(int v, int tl, int tr, int l, int r){
if(tl > r || l > tr) return make_pair(0, 0);
if(tl >= l && r >= tr) return t[v];
int mid = (tl + tr) / 2;
return f(get(v * 2, tl, mid, l, r), get(v * 2 + 1, mid + 1, tr, l, r));
}
void solve(){
int n, m;
cin >> n >> m;
pair<int, int> p[n + 1];
int s[m + 1];
vector<int> v;
for(int i = 1; i <= n; i++){
cin >> p[i].first >> p[i].second;
v.push_back(p[i].second);
}
for(int i = 1; i <= m; i++){
cin >> s[i];
}
v.push_back(-1);
sort(all(v));
v.erase(unique(all(v)), v.end());
int sz = v.size() - 1;
sort(p + 1, p + n + 1);
for(int i = 1; i <= n; i++){
p[i].second = lower_bound(all(v), p[i].second) - v.begin();
}
int ans = 0;
int suf[m + 2] = {};
for(int i = m; i >= 1; i--) suf[i] = max(suf[i + 1], s[i]);
auto find = [&](int x, int L){
int l = L + 1, r = m;
while(l <= r){
int mid = (l + r) / 2;
if(suf[mid] >= x) r = mid - 1;
else l = mid + 1;
}
return r + 1;
};
for(int i = 1; i <= n; i++){
auto [x, y] = get(1, 1, sz, 1, p[i].second);
int nxt = find(p[i].first, y);
if(nxt <= m && nxt > y) upd(1, 1, sz, p[i].second, x + 1, nxt);
// cout << p[i].second << ' ';
}
cout << t[1].first << '\n';
}
signed main(){
SS
// freopen("trains.in", "r", stdin);
// freopen("trains.out", "w", stdout);
int t = 1;
// cin >> t;
while(t--){
solve();
}
}
