#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#pragma GCC optimize("unroll-loops,no-stack-protector")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
using namespace __gnu_pbds;
using namespace std;
template <typename T>
using ordered_set = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
typedef long long ll;
typedef long double ld;
struct pic{
ll v,s;
bool operator <(const pic& rhs) const{
if (v == rhs.v){
return s < rhs.s;
}
return v < rhs.v;
}
};
vector <pic> arr;
vector <ll> frame;
ll ans = 0;
ll n,m;
int main(){
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cin >> n >> m;
arr.resize(n);
for (int z=0;z<n;z++){
cin >> arr[z].s >> arr[z].v;
}
frame.resize(m);
for (int z=0;z<m;z++){
cin >> frame[z];
}
sort(arr.rbegin(),arr.rend());
sort(frame.rbegin(),frame.rend());
ll i = 0;
for (int z=0;z<m && i < n;z++,i++){
while (i < n && arr[i].s > frame[z]){
i++;
}
if (i < n) ans++;
}
cout << ans << endl;
}
