#include <bits/stdc++.h>
#pragma GCC optimize("Ofast")
#pragma GCC target("avx,avx2,fma")
using namespace std;
#define int ll
#define FOR(i,s,e) for(ll i = s; i <= (ll)e; ++i)
#define DEC(i,s,e) for(ll i = s; i >= (ll)e; --i)
#define IAMSPEED ios_base::sync_with_stdio(false); cin.tie(0);
#define db(x) cerr << #x << "=" << x << "\n"
#define db2(x, y) cerr << #x << "=" << x << " , " << #y << "=" << y << "\n"
#define db3(a,b,c) cerr<<#a<<"="<<a<<","<<#b<<"="<<b<<","<<#c<<"="<<c<<"\n"
#define dbv(v) cerr << #v << ":"; for (auto ite : v) cerr << ite << ' '; cerr <<"\n"
#define dbvp(v) cerr << #v << ":"; for (auto ite : v) cerr << "{" << ite.f << ',' << ite.s << "} "; cerr << "\n"
#define dba(a,ss,ee) cerr << #a << ":"; FOR(ite,ss,ee) cerr << a[ite] << ' '; cerr << "\n"
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
#define ll long long
#define pb push_back
#define all(x) (x).begin(), (x).end()
#define f first
#define s second
#define reach cerr << "LINE: " << __LINE__ << "\n";
typedef pair <ll, ll> pi;
typedef tuple<ll,ll,ll> ti3;
string cts(char x) {string t(1,x); return t;}
ll rand(ll a, ll b) { return a + rng() % (b-a+1); }
const int MOD = 1e9 + 7;
const int inf = (int)1e9 + 500;
const long long oo = (ll)1e18 + 500;
template <typename T> void chmax(T& a, T b) { a = max(a, b); }
template <typename T> void chmin(T& a, T b) { a = min(a, b); }
const int MAXN = 100005;
#ifndef LOCAL
#define cerr if(0)cout
#endif
vector<pi>V[MAXN];
int32_t main()
{
IAMSPEED
int n,m; cin >> n >> m;
vector<pi>v;
FOR(i,1,n) {
int a,b; cin >> a >> b;
v.pb(pi(a,b));
}
vector<int> frames;
FOR(i,1,m) {
int x; cin >> x;
frames.pb(x);
}
sort(all(frames));
sort(all(v));
priority_queue<int>pq;
int idx=0;
multiset<pi,greater<pi>>ms;
FOR(i,0,frames.size()-1) {
int sz=frames[i];
while(idx<(int)v.size()&&v[idx].f<=sz){
V[i].pb(pi(v[idx].s,v[idx].f));
ms.insert(pi(v[idx].s,v[idx].f));
++idx;
}
}
int ans = 0;
DEC(i,frames.size()-1,0) {
if(ms.size()){
++ans;
ms.erase(ms.begin());
}
for(auto vv:V[i])if(ms.find(vv)!=ms.end())ms.erase(vv);
}
cout<<ans;
}
