#include <bits/stdc++.h>
#define int long long
#define FOR(i, a, b) for (int i = (a), _b = (b); i <= _b; ++i)
#define REV(i, a, b) for (int i = (a), _b = (b); i >= _b; --i)
using namespace std;
#define MAXN 100005
int n, m;
vector<pair<int, int>> a;
vector<int> b;
void solve(){
cin >> n >> m;
FOR(i, 1, n){
int s, v; cin >> s >> v;
a.push_back({v, s});
}
FOR(i, 1, m){
int x; cin >> x;
b.push_back(x);
}
sort(b.begin(), b.end(), greater<int>());
sort(a.begin(), a.end(), greater<pair<int, int>>());
int ptr = 0;
int res = 0;
for (int &x : b) {
while (ptr < (int)a.size() && a[ptr].second > x) ptr++;
if (ptr < (int)a.size()){
ptr++;
res++;
}
}
cout << res;
}
int32_t main(){
ios_base::sync_with_stdio(false);
cin.tie(nullptr); cout.tie(nullptr);
solve();
return 0;
}
