#include <bits/stdc++.h>
#define ll long long
#define ld long double
#define ff first
#define ss second
#define vl vector<long long>
#define vi vector<int>
#define pii pair<int,int>
#define pll pair<long long, long long>
#define pb push_back
#define rep(i, b) for(int i = 0; i < (b); ++i)
#define rep2(i,a,b) for(int i = a; i <= (b); ++i)
#define rep3(i,a,b,c) for(int i = a; i <= (b); i+=c)
#define count_bits(x) __builtin_popcountll((x))
#define all(x) (x).begin(),(x).end()
#define siz(x) (int)(x).size()
#define forall(it,x) for(auto& it:(x))
using namespace std;
//mt19937 mt;void random(){mt.seed(chrono::time_point_cast<chrono::milliseconds>(chrono::high_resolution_clock::now()).time_since_epoch().count());}
//ll rand(ll a, ll b) {return a + (mt() % (b-a+1));}
const int INF = 1e9+50;
const ll INF_L = 1e18+40;
const ll MOD = 1e9+7;
int main()
{
ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
//random();
int n,m;
cin >> n >> m;
vector<pii> paint;
rep(i,n)
{
int a,b;
cin >> a >> b;
paint.pb({b,a});
}
sort(all(paint));
reverse(all(paint));
multiset<int> frames;
rep(i,m)
{
int a;
cin >> a;
frames.insert(a);
}
int ans = 0;
rep(i,n)
{
if(siz(frames) == 0) break;
auto it = frames.end();
it--;
if(*it >= paint[i].ss)
{
ans++;
// cout << *it << " " << paint[i].ss << " " << paint[i].ff << " fr\n";
frames.erase(it);
}
}
cout << ans;
}
