#pragma GCC optimize("O3")
#include "bits/stdc++.h"
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace std;
using namespace __gnu_pbds;
typedef long long ll;
tree<int,int,greater<int>,rb_tree_tag,tree_order_statistics_node_update> map_t;
#define FOR(i, a, b) for (int i = (a); i < (b); i++)
#define F0R(i, a) for(int i = 0; i < (a); ++i)
#define sz(x) (int)x.size()
#define SORT(x) sort(x.begin(),x.end())
#define ERASE(x) x.erase(unique(x.begin(),x.end()),x.end())
#define POSL(x,v) (lower_bound(x.begin(),x.end(),v)-x.begin())
#define POSU(x,v) (upper_bound(x.begin(),x.end(),v)-x.begin())
#define REV(x) reverse(x.begin(),x.end())
int dx[]={-1,0,1,0};
int dy[]={0,-1,0,1};
int n,m;
const int mxN=1e5+5;
const int INF=2e9;
pair<int,int> arr[mxN];
int sizes[mxN];
int t[4*mxN],p[4*mxN];
void recalc(int v) {
if(t[2*v]<t[2*v+1]) {
t[v]=t[2*v];
p[v]=p[2*v];
}
else {
t[v]=t[2*v+1];
p[v]=p[2*v+1];
}
}
void build(int v,int tl,int tr) {
if(tl==tr) {
t[v]=arr[tl].second;
p[v]=tl;
return;
}
int mid=tl+(tr-tl)/2;
build(2*v,tl,mid);
build(2*v+1,mid+1,tr);
recalc(v);
}
pair<int,int> qry(int v,int tl,int tr,int l,int r) {
if(tr<l || tl>r)
return {-1,INF};
if(tl>=l && tr<=r)
return {p[v],t[v]};
int mid=tl+(tr-tl)/2;
pair<int,int> left=qry(2*v,tl,mid,l,r);
pair<int,int> right=qry(2*v+1,mid+1,tr,l,r);
if(left.second<right.second)
return left;
return right;
}
void upd(int v,int tl,int tr,int pos,int val) {
if(tr<pos || tl>pos)
return;
if(tl==tr) {
t[v]=val;
p[v]=pos;
return;
}
int mid=tl+(tr-tl)/2;
upd(2*v,tl,mid,pos,val);
upd(2*v+1,mid+1,tr,pos,val);
recalc(v);
}
int binSearch2(int val) {
int l,h;
l=0; h=n-1;
int res=-1;
while(l<=h) {
int mid=l+(h-l)/2;
if(arr[mid].first<=val) {
res=mid;
l=mid+1;
}
else
h=mid-1;
}
return res;
}
bool check(int val) {
vector<pair<int,int>> rem;
int prev=-1;
bool res=true;
FOR(i,m-val,m) {
int pos=binSearch2(sizes[i]);
if(pos==-1) {
res=false;
goto end;
}
pair<int,int> mn={-1,-1};
while(true) {
mn=qry(1,0,n-1,0,pos);
if(mn.second==INF) {
res=false;
goto end;
}
rem.push_back(mn);
upd(1,0,n-1,mn.first,INF);
if(mn.second>=prev)
break;
}
prev=mn.second;
}
end:;
for(auto p : rem)
upd(1,0,n-1,p.first,p.second);
return res;
}
int binSearch() {
int l,h;
l=0; h=min(m,n);
int res=0;
while(l<=h) {
int mid=l+(h-l)/2;
if(check(mid)) {
res=mid;
l=mid+1;
}
else
h=mid-1;
}
return res;
}
int main() {
// freopen("input.txt", "r", stdin);
// freopen("output.txt", "w", stdout);
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cin >> n >> m;
F0R(i,n)
cin >> arr[i].first >> arr[i].second;
F0R(i,m)
cin >> sizes[i];
sort(arr,arr+n);
sort(sizes,sizes+m);
build(1,0,n-1);
cout << binSearch();
return 0;
}
