#include <iostream>
#include <vector>
#include <set>
#include <iomanip>
#include <algorithm>
#include <functional>
#include <stdio.h>
#include <cmath>
#include <queue>
#include <string>
#include <map>
#include <fstream>
#include <complex>
#include <stack>
#include <set>
#define FOR(i,n) for(int i=0;i<n;i++)
#define FORE(i,a,b) for(int i=a;i<=b;i++)
#define ll long long int
#define vi vector<int>
#define ii pair<int,int>
#define pb push_back
#define mp make_pair
#define vv vector
#define ff first
#define ss second
#define pll pair<ll,ll>
#define cd complex<double>
#define ld long double
#define pld pair<ld,ld>
#define iii pair<ii,int>
using namespace std;
const int MAXN = 3000;
const int MAXK = 100+10;
int main(){
int n,m;
cin >> n >> m;
vi frames;
vv<ii> pics;
FOR(i,n){
int a,b;cin >> a >> b;
pics.pb({a,b});
}
FOR(i,m){
int a;cin >> a;
frames.pb(a);
}
sort(pics.begin(), pics.end(),greater<ii>());
sort(frames.begin(), frames.end(),greater<int>());
set<ii,greater<ii> > s;
int PTR = 0;
FOR(i,n){
s.insert({pics[i].ss,-i});
}
int ind = 0;
int ctr = 0;
int lst = 1e9+10;
while(ind < n and PTR < m and !s.empty()){
while(ind < n and pics[ind].ff > frames[PTR]){
ii x = {pics[ind].ss,-ind};
if(s.lower_bound(x) != s.end())s.erase(x);
ind++;
}
if(ind >= n)break;
// ======== //
//cout << ind << " " << PTR << endl;
while(!s.empty()){
ii x = *s.begin();
s.erase(s.begin());
if(x.ff <= lst){
lst = x.ff;
ctr++;
break;
}
}
// ======== //
PTR++;
}
cout << ctr << endl;
return 0;
}
