#include <bits/stdc++.h>
#pragma GCC optimize("Ofast")
#define AquA cin.tie(0);ios_base::sync_with_stdio(0);
#define fs first
#define sc second
#define cd complex<double>
#define p_q priority_queue
using namespace std;
int main(){
AquA;
int n,m;
cin >> n >> m;
vector<pair<int,int> > v(n);
vector<int> p(m);
for(int i=0;i<n;i++){
cin >> v[i].sc >> v[i].fs;
}
sort(v.begin(),v.end());
for(int i=0;i<m;i++){
cin >> p[i];
}
sort(p.begin(),p.end());
int nw=m-1;
int ans=0;
for(int i=n-1;i>=0;i--){
if(nw>=0 && p[nw]>=v[i].sc){
ans++;
nw--;
}
}
cout << ans << "\n";
return 0;
}
