#include <bits/stdc++.h>
#define ll long long
#define pb push_back
#define mp make_pair
#define P pair<ll, ll>
using namespace std;
const int maxn = 100100;
vector<P>v;
ll frames[maxn], n, m;
int bin_search(ll x) {
if(x > frames[m]) return 0;
int index = m;
for(int cekor=m/2;cekor>0;cekor/=2) {
while(index-cekor >= 1 && frames[index-cekor] >= x) index-=cekor;
}
return m - index + 1;
}
int main() {
ios_base::sync_with_stdio(false);
cin.tie(0);
cin>>n>>m;
ll sz, va;
for(int i=1;i<=n;i++) {
cin>>sz>>va;
v.pb(mp(va, sz));
}
v.pb(mp(0, 0));
sort(v.begin(), v.end());
for(int i=1;i<=m;i++) {
cin>>frames[i];
}
sort(frames+1, frames+m+1);
int result = 0;
int reached = 0;
for(int i=n;i>=1;i--) {
// process reversed
int fit = bin_search(v[i].second);
if(fit > reached) {
// extend reached
reached++;
result = max(result, reached);
}
}
cout<<result<<"\n";
return 0;
}
