// #include <bits/stdc++.h>
#include <iostream>
#include <cmath>
#include <algorithm>
#include <map>
#include <vector>
#include <iomanip>
#include <string>
#include <queue>
#include <set>
#include <deque>
#include <numeric>
#include <stack>
#include <chrono>
using namespace std;
void fast_io(){
// freopen("", "r", stdin);
// freopen("", "w", stdout);
ios::sync_with_stdio(0);
cin.tie(); cout.tie();
cout << setprecision(9);
}
#define int long long
#define endl '\n'
#define all(v) (v).begin(), (v).end()
#define rall(v) (v).rbegin(), (v).rend()
#define fi first
#define se second
void solve() {
int n, m; cin >> n >> m;
int S[n + 1], V[n + 1], C[m + 1];
vector<pair<int, int>> p;
set<int> s;
for (int i = 1; i <= n; i++) {
cin >> S[i] >> V[i];
p.push_back({S[i], V[i]});
}
for (int i = 1; i <= m; i++) cin >> C[i];
sort(all(p));
sort(C + 1, C + m + 1);
int idx = 1, lst = 0, ans = 0;
for (int i = 1; i <= m; i++){
while (idx <= n && p[idx].fi <= C[i]){
s.insert(p[idx].se);
idx++;
}
while (s.size() && *s.begin() < lst) s.erase(s.begin());
if (s.size()){
ans++;
lst = *s.begin();
s.erase(s.begin());
}
}
cout << ans << endl;
return;
}
signed main() {
fast_io();
srand(chrono::steady_clock::now().time_since_epoch().count());
int tc = 1;
// cin >> tc;
while (tc--) solve();
return 0;
}
