#include "bits/stdc++.h"
#define fast ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
#define ll long long
#define pb push_back
#define in insert
#define F first
#define S second
#define vll vector<ll>
#define all(v) v.begin(),v.end()
#define endl '\n'
#define pii pair<ll,ll>
#define yes cout << "YES" << endl;
#define no cout << "NO" << endl;
using namespace std;
const ll INF = 1e18, mod = 1e9 + 7, N = 2e5 + 5;
ll gcd(ll a, ll b){
if(b == 0){
return a;
}
return gcd(b, a%b);
}
ll lcm(ll a, ll b){
return (a / gcd(a,b)) * b;
}
void solve(){
ll n,m;
cin >> n >> m;
vector<pii>v;
ll x,y;
for(int i = 0; i < n; i++){
cin >> x >> y;
v.pb({y,x});
}
vector<ll>f;
ll r;
for(int i = 0; i < m; i++){
cin >> r;
f.pb(r);
}
sort(all(v));
ll cnt = 0;
for(int i = 0; i < v.size(); i++){
auto it = lower_bound(all(f), v[i].S);
// cout << *it << endl;
if(it == f.end()){
cout << cnt << endl;
return;
}
cnt++;
f.erase(it);
}
cout << cnt << endl;
}
int main() {
fast;
ll t = 1;
//cin >> t;
while(t--){
solve();
}
return 0;
}
