#include "bits/stdc++.h"
using namespace std;
#define ll long long
#define endl '\n'
const ll MOD = 1e9+7;
const ll INF = 1e16;
const ll MAX = 2 * 1e5;
void solve(){
int n,m;
cin>>n>>m;
vector<pair<int,int>> photos(n);
vector<int> frames(m);
for(int i = 0; i < n; i++){
int a,b; cin>>a>>b;
photos[i] = {b,a};
}
sort(photos.begin(), photos.end());
for(int i = 0; i < m; i++){
cin>>frames[i];
}
sort(frames.begin(), frames.end());
int ans = 0;
while(!photos.empty() && !frames.empty()){
if(photos[photos.size()-1].second <= frames[frames.size()-1]){
ans++;
photos.pop_back();
frames.pop_back();
}else{
photos.pop_back();
}
}
cout<<ans;
}
int main()
{
cin.tie(NULL);
ios::sync_with_stdio(NULL);
int t = 1;
//cin >> t;
while(t--){
//cout<<"Case #"<<t<<" > "<<endl;
solve();
cout<<endl;
}
}
