#include <bits/stdc++.h>
#define pb push_back
#define ins isnert
#define pii pair<int,int>
#define ff first
#define ss second
#define loop(i,a,b) for(int i = (a); i < (b); i ++)
#define op(x) cerr << #x << " = " << x << endl;
#define opa(x) cerr << #x << " = " << x << ", ";
#define ops(x) cerr << x;
#define spac cerr << ' ';
#define entr cerr << endl;
#define STL(x) cerr << #x << " : "; for(auto &qwe:x) cerr << qwe << ' '; cerr << endl;
#define ARR(x, nnn) cerr << #x << " : "; loop(qwe,0,nnn) cerr << x[qwe] << ' '; cerr << endl;
#define BAE(x) (x).begin(), (x).end()
using namespace std;
const int mxn = (int)(1e5) + 10;
struct P{
int sz, val;
void read(){
cin >> sz >> val;
}
bool operator<(P x){
return sz < x.sz;
}
}a[mxn];
int b[mxn];
vector<int> can_val[mxn];
bool check(int n, int m, int start){
priority_queue<int, vector<int>, greater<int>> pq;
int pre = -1;
loop(i,1,start){
for(auto &j:can_val[i]){
pq.push(j);
}
}
bool now_can;
loop(i,start,m+1){
now_can = false;
for(auto &j:can_val[i]){
pq.push(j);
}
while(!pq.empty()){
if(pq.top() < pre) pq.pop();
else{
now_can = true;
pre = pq.top();
pq.pop();
break;
}
}
if(!now_can) return false;
}
return true;
}
int main(){
ios::sync_with_stdio(false); cin.tie(0);
int n, m;
cin >> n >> m;
loop(i,1,n+1){
a[i].read();
}
sort(a + 1, a + (n + 1));
loop(i,1,m+1){
cin >> b[i];
}
sort(b + 1, b + (m + 1));
bool have_ans = false;
for(int i = 1, j = 1; i <= n && j <= m; ){
// opa(i) op(j)
if(a[i].sz <= b[j]){
can_val[j].pb(a[i].val);
i++;
have_ans = true;
}
else j++;
}
if(!have_ans){
cout << "0\n";
return 0;
}
int l = 1, r = m, mid;
while(l < r){
mid = (l + r) >> 1;
if(check(n, m, mid)){
r = mid;
}
else{
l = mid + 1;
}
}
cout << m - l + 1 << '\n';
}
