#include <bits/stdc++.h>
using namespace std;
#define int long long
#define OYY LLONG_MAX
#define faster ios_base::sync_with_stdio(false);cin.tie(NULL);cout.tie(NULL);
#define fi first
#define se second
#define FOR for(int i=1;i<=n;i++)
#define mid (start+end)/2
#define pb push_back
#define lim 200005
#define N 500050
typedef long long lo;
const int mod=1000000007;
int n,m;
int pic[lim][2];
int tut[lim];
vector<pair<int,int>> v;
int32_t main(){
faster
cin>>n>>m;
FOR{
cin>>pic[i][0]>>pic[i][1];
v.pb({pic[i][1],pic[i][0]});
}
sort(v.begin(),v.end());
for(int i=1;i<=m;i++){
cin>>tut[i];
}
sort(tut+1,tut+1+m);
int ind=0;
for(int i=1;i<=m;i++){
if(v[ind].se<=tut[i]){
ind++;
}
}
cout<<ind<<'\n';
return 0;
}
