#include<bits/stdc++.h>
#define int long long
using namespace std;
int s[100005];
int v[100005];
vector<int>c;
vector<pair<int,int>>pic;
int32_t main(){
ios_base::sync_with_stdio(false);
cin.tie(0);
int n,m;cin>>n>>m;
for(int i=1;i<=n;i++)cin>>s[i]>>v[i],pic.push_back({v[i],s[i]});
for(int i=1;i<=m;i++){
int temp;cin>>temp;
c.push_back(temp);
}
sort(c.begin(),c.end());
sort(pic.begin(),pic.end());
reverse(pic.begin(),pic.end());
int ans=0;
for(auto x:pic){
if(c.empty())break;
if(x.second<=c.back())c.pop_back(),ans++;
}
cout<<ans;
}
