#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<ll,ll> pi;
typedef vector <ll> vi;
typedef vector <pi> vpi;
#define f first
#define s second
#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 pb push_back
#define all(x) (x).begin(), (x).end()
#define lbd(x, y) lower_bound(all(x), y)
#define ubd(x, y) upper_bound(all(x), y)
#define aFOR(i,x) for (auto i: x)
#define mem(x,i) memset(x,i,sizeof x)
#define fast ios_base::sync_with_stdio(false),cin.tie(0)
#define maxn 100001
#define int ll
int B[maxn];
pi A[maxn];
int N,M;
int32_t main(){
fast;
cin>>N>>M;
priority_queue <int> pq;
FOR(i,0,N-1) cin>>A[i].s>>A[i].f;
FOR(i,0,M-1){
int a;
cin>>a;
pq.push(a);
}
sort(A,A+N,greater<pi>());
sort(B,B+N,greater<int>());
int ans = 0;
FOR(i,0,N-1){
if (!pq.empty() && pq.top() >= A[i].s){
ans++;
pq.pop();
}
}
cout<<ans;
}
