#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ld = long double;
using db = double;
using str = string;
using ii = pair<int,int>;
using pl = pair<ll,ll>;
using pd = pair<db,db>;
using vi = vector<int>;
using vb = vector<bool>;
using vl = vector<ll>;
using vd = vector<db>;
using vs = vector<str>;
using vii = vector<ii>;
using vpl = vector<pl>;
using vpd = vector<pd>;
#define tcT template<class T
#define tcTU tcT, class U
tcT> using V = vector<T>;
tcT, size_t SZ> using AR = array<T,SZ>;
tcT> using PR = pair<T,T>;
// pairs
#define mp make_pair
#define f first
#define s second
#define FOR(i,a,b) for (int i = (a); i < (b); ++i)
#define F0R(i,a) FOR(i,0,a)
#define ROF(i,a,b) for (int i = (a)-1; i >= (b); --i)
#define R0F(i,a) ROF(i,a,0)
#define trav(a,x) for (auto& a: x)
#define len(x) int((x).size())
#define bg(x) begin(x)
#define all(x) bg(x), end(x)
#define rall(x) rbegin(x), rend(x)
#define sor(x) sort(all(x))
#define rsz resize
#define ins insert
#define ft front()
#define bk back()
#define pb push_back
#define eb emplace_back
#define pf push_front
const int MOD = 1e9+7; // 998244353;
const int MX = 2e5+5;
const ll INF = 1e18; // not too close to LLONG_MAX
const ld PI = acos((ld)-1);
const int dx[4] = {1,0,-1,0}, dy[4] = {0,1,0,-1}; // for every grid problem!!
vector<pair<ll, ll>> pics;
vector<ll> frames;
bool doesWork(ll n_frames){
ll cur_frame = 0;
if (cur_frame == n_frames) return 1;
trav(pic, pics){
if (pic.f <= frames[cur_frame]){
cur_frame++;
}
if (cur_frame == n_frames) return 1;
}
return 0;
}
int main(){
std::ios::sync_with_stdio(false); cin.tie(NULL);
int N, M; cin >> N >> M;
F0R(_, N){
ll s, v; cin >> s >> v; pics.pb({s,v});
}
F0R(_, M){
ll c; cin >> c; frames.pb(c);
}
sort(all(frames), [](ll& n1, ll& n2)->bool{return n1 > n2;}); // bigger is better
sort(all(pics), [](pair<ll,ll>&p1, pair<ll,ll>&p2)->bool{
if (p1.s == p2.s) { return p1.f > p2.f;} return p1.s > p2.s;
});
//trav(i, pics) cout << i.f << " " << i.s << " ";
//cout << endl;
for(int x=M; x>=0; x--){
if (doesWork(x)){
cout << x << endl;
return 0;
}
}
cout << doesWork(2)<< endl;
}
