#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;z
#define pb push_back
#define ff first
#define ss second
#define all(x) x.begin(),x.end()
#define rall(x) x.rbegin(),x.rend()
#define int long long
//#define ordst tree<pair<int,int>, null_type, less<pair<int,int>>, rb_tree_tag , tree_order_statistics_node_update >
//#define double long double
template <class F, class _S>
bool chmin(F &u, const _S &v){
bool flag = false;
if ( u > v ){
u = v; flag |= true;
}
return flag;
}
template <class F, class _S>
bool chmax(F &u, const _S &v){
bool flag = false;
if ( u < v ){
u = v; flag |= true;
}
return flag;
}
const int N = (1<<18) +1, inf = 1e18+200;
//int mod = 998244353;
//int mod = 1000000007;
//mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
//#define rnd(l, r) uniform_int_distribution <int> (l, r)(rng)
void solve(){
int n, m;
cin >> n >> m;
vector<array<int,2>> pic(n);
for(auto &[i, j]:pic)cin >> j >> i;
vector<int> siz(m);
for(int &i:siz)cin >> i;
sort(all(pic));sort(all(siz));
auto ok = [&](int x) -> bool{
int it = 0;
for(int i = m-x; i < m; i ++){
while(it < n && siz[i] < pic[it][1])it++;
if(it == n)return false;
it++;
}
return true;
};
int l = 0, r = min(n,m)+1;
while(l+1 < r){
int mid = (l+r)>>1;
if(ok(mid))l = mid;
else r = mid;
}
cout << l << '\n';
}
signed main(){
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
cout.tie(nullptr);
int tt = 1;
//cin >> tt;
while(tt--){
solve();
}
}
