#pragma GCC target("avx2,bmi,bmi2,lzcnt,popcnt")
#pragma GCC optimize("O3,unroll-loops")
#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#define all(v) v.begin(), v.end()
#define pb push_back
#define ss second
#define ff first
#define vt vector
using namespace std;
using namespace __gnu_pbds;
typedef long long ll;
typedef pair<int, int> pii;
typedef tree<int, null_type, less<int>, rb_tree_tag, tree_order_statistics_node_update> ordered_set;
const int inf = 1e9;
const int mod = 1e9+7;
const int maxn = 1e5 + 1;
void solve() {
int n, m;
cin >> n >> m;
pii a[n];
for(int i = 0; i < n; i++){
cin >> a[i].ff >> a[i].ss;
}
sort(a, a + n);
int c[m];
for(int i = 0; i < m; i++){
cin >> c[i];
}
sort(c, c + m);
int l = 0, r = m + 1;
while(l + 1 < r){
int mid = l + (r - l) / 2;
int xl = 0, prev = 0;
multiset<int> ms;
bool ok = 1;
for(int i = m - mid; i < m; i++){
while(xl < n && a[xl].ff <= c[i])ms.insert(a[xl].ss), xl++;
while(!ms.empty() && prev > *ms.begin())ms.erase(ms.begin());
if(ms.empty()){
ok = 0;
break;
}
prev = *ms.begin();
ms.erase(ms.begin());
}
if(ok)l = mid;
else r = mid;
}
cout << l;
}
int main() {
ios_base::sync_with_stdio(0);
cin.tie(0);
int times = 1;
//cin >> times;
for(int i = 1; i <= times; i++) {
solve();
}
return 0;
}
