#include <bits/stdc++.h>
using namespace std;
#define int long long
#define FOR(i,a,b) for (int i = (a); i < (b); ++i)
#define pb push_back
#define all(a) a.begin(), a.end()
#define endl "\n"
void printVector(vector<int> a){
for (auto x: a) cout << x << " ";
cout << endl;
}
void solve(){
int n, m; cin >> n >> m;
vector<pair<int, int>> o(n);
FOR(i,0,n){
cin >> o[i].second >> o[i].first;
}
sort(all(o));
vector<int> frames(m);
FOR(i,0,m) cin >> frames[i];
sort(all(frames));
int ans = 0;
int curr = m-1;
for (int i = n-1; i >= 0; i--){
if (curr >= 0 && o[i].second <= frames[curr]){
curr--;
ans++;
}
}
cout << ans << endl;
}
int32_t main(){
ios::sync_with_stdio(false);cin.tie(nullptr);
int t = 1; // cin >> t;
while (t--) solve();
}
