#include <bits/stdc++.h>
#define pb push_back
#define f first
#define sc second
using namespace std;
typedef long long int ll;
typedef string str;
struct segtree{
struct node{
int in; ll mx;
node(){
mx = 0;
}
node(int _in, ll x){
in = _in;
mx = x;
}
node operator+(node a){
return (a.mx >= mx ? node(a.in, a.mx):node(in, mx));
}
};
int k;
vector<node> v;
segtree(int n){
k = 1;
while(k < n) k*=2;
k*=2;
v.resize(k);
for(int i = k-1; i >= k/2; i--) v[i].in = i-k/2;
for(int i = k/2-1; i > 0; i--) v[i] = v[2*i]+v[2*i+1];
}
void upd(int in, ll x){
in+=k/2;
v[in].mx = x;
in/=2;
while(in > 0){
v[in] = v[2*in]+v[2*in+1];
in/=2;
}
}
pair<ll, int> smx(int l, int r, int nd, int a, int b){
if(a > r || b < l) return {-1, -1};
if(a >= l && b <= r) return {v[nd].mx, v[nd].in};
int md = (a+b)/2;
return max(smx(l, r, 2*nd, a, md), smx(l, r, 2*nd+1, md+1, b));
}
pair<ll, int> smx(int l, int r){
return smx(l, r, 1, 0, k/2-1);
}
};
int main(){
ios_base::sync_with_stdio(0);
cin.tie(0);
int n, m; cin >> n >> m;
vector<pair<ll, ll>> pics(n);
vector<ll> frames(m), bs;
for(auto &p: pics) cin >> p.f >> p.sc, bs.pb(-p.f);
for(ll &x: frames) cin >> x;
sort(pics.begin(), pics.end());
sort(bs.begin(), bs.end());
sort(frames.begin(), frames.end());
segtree seg(n);
for(int i = 0; i < n; i++) seg.upd(i, pics[i].sc);
int ans = 0;
for(int i = m-1; i >= 0; i--){
auto it = lower_bound(bs.begin(), bs.end(), -frames[i]);
int in = n-1-(it-bs.begin());
if(in == -1) continue;
auto p = seg.smx(0, in);
if(p.f == 0) continue;
ans++;
seg.upd(p.sc, 0);
}
cout << ans << "\n";
}
