#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace std;
using namespace __gnu_pbds;
#pragma GCC optimize("O3,unroll-loops")
#pragma GCC target("avx2,bmi,bmi2,lzcnt,popcnt")
#define ll long long
#define ull unsigned long long
#define ld long double
#define pll pair<ll, ll>
#define pii pair<int, int>
#define coutpair(p) cout << p.first << " " << p.second << "|"
template<class T> using ordered_set = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
template<class T> using ordered_multiset = tree<T, null_type, less_equal<T>, rb_tree_tag, tree_order_statistics_node_update>;
//greedy idea : put the largest value picture that can fit into the ith frame, starting from the largest frame.
int main(){
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
ll n, m; cin >> n >> m;
priority_queue<pll> pq; //{value, size}
for (int i=0; i<n; i++){
ll s, v; cin >> s >> v;
pq.push({v, s});
}
ll c[m];
for (int i=0; i<m; i++) cin >> c[i];
sort(c, c+m, greater<ll>());
ll val[m];
for (int i=0; i<m; i++){
while (c[i] < pq.top().second && !pq.empty()) pq.pop();
if (pq.empty()){
cout << i;
return 0;
}
val[i] = pq.top().first; pq.pop();
if (i == 0) continue;
if (val[i] > val[i-1]){
cout << i;
return 0;
}
}
cout << m;
return 0;
}
