// #pragma GCC optimize("Ofast,unroll-loops")
// #pragma comment(linker, "/stack:200000000")
// #pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,avx2,fma,tune=native")
#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace std;
using namespace __gnu_pbds;
typedef int ll;
typedef long double ld;
typedef pair <ll, ll> pll;
#ifdef SINA
#define dbg(...) __f(#__VA_ARGS__, __VA_ARGS__)
template <typename Arg1> void __f(const char* name, Arg1&& arg1) { cout << name << " : " << arg1 << std::endl; }
template <typename Arg1, typename... Args> void __f (const char* names, Arg1&& arg1, Args&&... args) {
const char* comma = strchr(names + 1, ',');cout.write(names, comma - names) << " : " << arg1<<" | ";__f(comma+1, args...); }
#define dbg2(x, j, n) cout<< #x << " : "; output((j), (n), x, 1); cout.flush();
#else
#define dbg(...) 0
#define dbg2(x, j, n) 0
#endif
#define SZ(x) ((ll)((x).size()))
#define File(s, t) freopen(s ".txt", "r", stdin); freopen(t ".txt", "w", stdout);
#define input(j, n, a) for (int _i = (j); _i < (n)+(j); _i++) cin>> a[_i];
#define output(j, n, a, t) for (int _i = (j); _i < (n)+(j); _i++) cout<< a[_i] << (((t) && _i != (n)+(j)-1)? ' ' : '\n');
#define kill(x) return cout<< x << endl, 0
#define cl const ll
#define fr first
#define sc second
#define lc (v << 1)
#define rc (lc | 1)
#define mid ((l + r) >> 1)
#define All(x) (x).begin(), (x).end()
cl inf = sizeof(ll) == 4 ? (1e9 + 10) : (3e18), mod = 1e9 + 7, MOD = 998244353;
template <class A,class B> ostream& operator << (ostream& out,const pair<A,B>&a){return out<<'('<<a.first<<", "<<a.second<<')';}
template <class A> ostream& operator << (ostream& out, const vector<A> &a) {
out<< '['; for (int i = -1; ++i < int(a.size());) out<< a[i] << (i + 1 < int(a.size()) ? ", " : ""); return out<<']'; }
template <class T, typename _t = less <T> > using Tree = tree <T, null_type, _t, rb_tree_tag, tree_order_statistics_node_update>;
cl N = 1e5 + 7;
ll fsz [N], id [N], n, m, ans;
vector <ll> vec;
pll pic [N];
struct seg {
ll l, r;
pll mx;
seg *lt, *rt;
inline seg (cl &L = 1, cl &R = N - 2) : l(L), r(R) {}
void build () {
if (l == r) {
mx = {pic[l].sc, l};
return;
}
lt = new seg (l, mid);
rt = new seg (mid + 1, r);
lt->build();
rt->build();
mx = max(lt->mx, rt->mx);
}
void upd (cl &pos) {
if (l == r) {
mx.fr = -inf;
return;
}
if (pos <= mid) lt->upd(pos);
else rt->upd(pos);
mx = max(lt->mx, rt->mx);
}
pll ask (cl &ql, cl &qr) {
if (r < ql || qr < l) return pll(-inf, -inf);
if (ql <= l && r <= qr) return mx;
return max(lt->ask(ql, qr), rt->ask(ql, qr));
}
} mytree;
int main ()
{
ios::sync_with_stdio(false); cin.tie(0); cout.tie(0);
iota(id, id + N, 0);
cin>> n >> m;
for (ll i = 1; i <= n; i++) cin>> pic[i].fr >> pic[i].sc, vec.push_back(pic[i].fr);
for (ll i = 1; i <= m; i++) cin>> fsz[i];
sort(All(vec));
sort(fsz + 1, fsz + m + 1, greater<ll>());
sort(pic + 1, pic + n + 1);
mytree.r = n; mytree.build();
sort(id + 1, id + n + 1, [&](ll x, ll y) { return pic[x].sc > pic[y].sc; });
for (ll i = 1, R = 1; i <= m; i++) {
auto x = mytree.ask(1, upper_bound(All(vec), fsz[i]) - vec.begin());
// dbg(x);
if (x.fr == -inf) continue;
ans++;
mytree.upd(x.sc);
while (R <= n && pic[id[R]].sc > x.fr) mytree.upd(id[R++]);
}
kill(ans);
return 0;
}
/*
3 4
10 20
5 1
3 5
4
6
10
4
3 2
1 2
1 2
1 2
1
1
4 2
28 1
8 8
6 10
16 9
4
3
8 8
508917604 35617051
501958939 840246141
485338402 32896484
957730250 357542366
904165504 137209882
684085683 775621730
552953629 20004459
125090903 607302990
433255278
979756183
28423637
856448848
276518245
314201319
666094038
149542543
*/
