#include <bits/stdc++.h>
using namespace std;
#define pb push_back
#define mp make_pair
typedef long long ll;
typedef pair<long long, long long> pll;
typedef pair<int,int> pii;
typedef vector<long long> vl;
typedef vector<int> vi;
int n, m;
vector<pll> arr;
vl frame;
bool can(int x){
int j = 1, prev = 0;
priority_queue<int, vector<int>, greater<int>> pq;
for(int i = m-x+1; i <= m; i++){
while(j <= n && arr[j].first <= frame[i]){
pq.push(arr[j].second);
j++;
}
if(pq.empty()) return false;
else{
while(!pq.empty() && (pq.top() < prev)){
pq.pop();
}
if(pq.empty()) return false;
else{
prev = pq.top();
pq.pop();
}
}
}
return true;
}
int main(){
cin>>n>>m;
arr.resize(n+1);
frame.resize(m+1);
for(int i = 1; i <= n; i++){
cin>>arr[i].first>>arr[i].second;
}
for(int i = 1; i <= m; i++){
cin>>frame[i];
}
sort(frame.begin(), frame.end());
sort(arr.begin(), arr.end());
int l = 1, r = min(n, m), ans = 0;
while(l <= r){
int mid = (l + r) / 2;
bool can1 = can(mid);
if(can1){
ans = mid;
l = mid + 1;
}
else
r = mid - 1;
}
cout<<ans<<endl;
return 0;
}
