#include<bits/stdc++.h>
using namespace std;
using ll = long long;
struct obj{
ll s,v,i;
bool operator<(const obj &o) const{
return v!=o.v?v<o.v:s<o.s;
}
};
int main(){
ios::sync_with_stdio(0);cin.tie(0);
ll n,m;
cin >> n >> m;
vector<ll> c(m);
vector<obj> a(n);
for(obj &o : a) cin >> o.s >> o.v;
for(ll &i : c) cin >> i;
sort(a.begin(),a.end());
sort(c.begin(),c.end());
for(obj &o : a){
o.i = c.end()-lower_bound(c.begin(),c.end(),o.s);
}
reverse(a.begin(),a.end());
ll ans = 0;
for(obj &o : a){
ans = max(ans,min(ans+1,o.i));
}
cout << ans << "\n";
}
