#include <bits/stdc++.h>
using namespace std;
#define int long long
#define fi first
#define se second
#define pii pair<int,int>
#define pb push_back
const int mn=1e5+5;
struct pt{
int s,v;
bool operator < (const pt &o) const{
if (v!=o.v)return v<o.v;
return s<o.s;
}
friend istream& operator >> (istream& in,pt& p){
in>>p.s>>p.v;
return in;
}
};
pt p[mn];
int f[mn];
signed main(){
//freopen("","r",stdin);
//freopen("","w",stdout);
ios_base::sync_with_stdio(0);
cin.tie(0);
int n,m;
cin>>n>>m;
for (int i=1;i<=n;i++){
cin>>p[i];
}
for (int i=1;i<=m;i++){
cin>>f[i];
}
sort(p+1,p+n+1);
sort(f+1,f+m+1);
int it=n;
int ans=0;
for (int i=m;i>=1;i--){
while (it&&p[it].s>f[i]) it--;
if (!it) break;
if (p[it].s<=f[i]) ans++;
it--;
}
cout<<ans;
}
