#include<bits/stdc++.h>
using namespace std;
#define INF 1e9
#define MAX 100005
#define xx first
#define yy second
#define pb push_back
#define mp make_pair
#define ull long long
#define FOR(i,a,b) for(int i=a;i<=b;i++)
#define nl '\n'
#define zai <<' '<<
#define all(a) a.begin(),a.end()
#define pc __builtin_popcount
#define debug(args...) cerr << #args << " = "; Dbg,args; cerr << nl;
struct Dbg { template<typename T> Dbg& operator,(const T& v) { cerr << v << ", "; return *this; } } Dbg;
template <typename T> ostream& operator<<(ostream& _o_, const vector<T>& _v_){
if(!_v_.empty()){_o_<<'[';copy(_v_.begin(),_v_.end(),ostream_iterator<T>(_o_,", "));_o_<<"\b\b]";}return _o_;}
typedef vector<int> vi;
typedef pair<int,int> ii;
typedef vector<ii> vii;
typedef priority_queue<int, vector<int>, greater<int>> minheap;
template<class C> void mini(C &_a, C _b) { _a = min(_a, _b); }
template<class C> void maxi(C &_a, C _b) { _a = max(_a, _b); }
vii a;
vi b;
int n, m;
bool check(int x){
minheap q;
int j = 0, left = -1;
bool ok = 1;
for(int i = m - x; i < m; i++){
while(j < n && a[j].first <= b[i]){
if(a[j].second >= left)q.push(a[j].second);
j++;
}
if(q.empty())return 0;
left = q.top();
q.pop();
}
return 1;
}
vi scn(int n){
vi a(n);
for(int i = 0; i < n; i++){
cin >> a[i];
}
return a;
}
int main(){
ios_base::sync_with_stdio(false);cin.tie(0);cout.tie(0);
cin >> n >> m;
for(int i = 0; i < n; i++){
int c, v;
cin >> c >> v;
a.emplace_back(c, v);
}
b = scn(m);
sort(all(a)); sort(all(b));
int l = 0, r = min(n, m);
while(l != r){
int mid = (l + r + 1) >> 1;
if(check(mid)){
l = mid;
}
else{
r = mid - 1;
}
}
cout << l;
return 0;
}
