#include<bits/stdc++.h>
using namespace std;
#define INIT ios_base :: sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL);mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
#define mp make_pair
#define pb push_back
#define ft first
#define sc second
#define ll long long
#define pii pair<int, int>
#define count_bits __builtin_popcount
#define int ll
int t, n, m, s[100010], v[100010], c[100010];
pii pr[100010];
map<pii, vector<int>> h;
bool pos[100010];
multiset<pii> ms;
int32_t main(){
INIT
cin>>n>>m;
for(int i=1; i<=n; i++){
cin>>s[i]>>v[i];
ms.insert({v[i], s[i]});
pr[i]={s[i], v[i]};
}
sort(pr+1 , pr+1+n);
for(int i=1; i<=n; i++){
pos[i]=true;
h[pr[i] ].pb(i);
}
for(int i=1; i<=m ;i++){
cin>>c[i];
}
sort(c+1, c+1+m);
int pt=n;
int res=0;
for(int i=m; i>=1; i--){
while( (pt>=1) && ( (pos[pt]==false) || (pr[pt].ft>c[i]) ) ){
if(pos[pt]==false){
pt--; continue;
}
ms.erase(ms.find({pr[pt].sc, pr[pt].ft}) );
pt--;
}
if(pt>=1){
res++;
auto it=ms.end();
it--;
int loc=(h[ make_pair(it->sc, it->ft) ].back() ); h[ make_pair(it->sc, it->ft) ].pop_back(); pos[loc]=false;
ms.erase(it);
}
else{
break;
}
}
cout<<res;
return 0;
}
