#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define MAXN (1000005)
int main(){
ios_base::sync_with_stdio(false);cin.tie(0);
ll N,M;
cin>>N>>M;
pair<ll,ll> arr[N]; //s, v
for(ll i = 0;i < N;i++){
cin>>arr[i].first>>arr[i].second;
}
ll C[M];
for(ll i = 0;i < M;i++){
cin>>C[i];
}
sort(arr,arr + N);
sort(C,C + M);
priority_queue<pair<ll,ll> > pq;
ll ptr = -1;
while(ptr < N - 1 && arr[ptr + 1].first <= C[M - 1]){
ptr++;
pq.push(make_pair(arr[ptr].second,arr[ptr].first));
}
ll ans = 0;
ll prev = 1e18;
for(ll i = M - 1;i >= 0;i--){
while(!pq.empty() && (pq.top().first > prev || pq.top().second > C[i])){
pq.pop();
}
if(!pq.empty()){
ans++;
pq.pop();
}
}
cout<<ans<<'\n';
}
