#include<bits/stdc++.h>
using namespace std;
#define int long long
#define oo 10000000000000001
int n,m,c[100005];
int v[100005],s[100005],srtv[100005],seqv[100005],seqs[100005],seq[100005],pos,ans; //v.s->v,pos
signed main(){
ios::sync_with_stdio(0),cin.tie(0);
cin>>n>>m;
for(int i=1;i<=n;i++){
cin>>s[i]>>v[i];
srtv[i]=-v[i];
}
for(int i=1;i<=m;i++){
cin>>c[i];
c[i]=-c[i];
}
sort(c+1,c+m+1),sort(srtv+1,srtv+n+1);
for(int i=1;i<=n;i++){
seqs[i]=upper_bound(c+1,c+m+1,-s[i])-c-1;
}
for(int i=1;i<=n;i++){
seqv[i]=upper_bound(srtv+1,srtv+n+1,-v[i])-srtv-1;
seq[i]=min(seqv[i],seqs[i]);
}
sort(seq+1,seq+n+1);
reverse(seq+1,seq+n+1);
pos=1000000000000000000;
ans=0;
for(int i=1;i<=n;i++){
pos=min(pos-1,seq[i]);
if(pos<=0) break;
ans++;
}
cout<<ans<<'\n';
return 0;
}
