#include <bits/stdc++.h>
#pragma GCC target("avx2")
#pragma GCC optimize("O3,unroll-loops")
using namespace std;
#define int long long
#define pii pair<int,int>
#define ff first
#define ss second
#define sp << " " <<
#define all(cont) cont.begin(),cont.end()
#define vi vector<int>
const int inf = 1e18,N = 3e5+1,MOD = 998244353,B = 250;
vi val(N);
struct ST {
vi t;
void build(int node,int l,int r) {
if (l == r) {
t[node]= val[l];
return;
}
int m = (l+r) >> 1;
build(2*node,l,m),build(2*node+1,m+1,r);
t[node] = min(t[2*node],t[2*node+1]);
}
ST(int nn) {
t.resize(4*nn+1,0);
build(1,1,nn);
}
int query(int node,int l,int r,int v) {
if (t[node] > v) return 0;
if (l == r) return l;
int m = (l+r) >> 1;
int q = query(2*node+1,m+1,r,v);
if (!q) return query(2*node,l,m,v);
return q;
}
int walk(int node,int l,int r,int L,int R,int v) {
if (l > R || r < L) return 0;
if (t[node] > v) return 0;
if (l >= L && r <= R) return query(node,l,r,v);
int m = (l+r) >> 1;
int w = walk(2*node+1,m+1,r,L,R,v);
if (!w) return walk(2*node,l,m,L,R,v);
return w;
}
};
void solve() {
int n,m;
cin >> n >> m;
vi s(n+1),v(n+1);
for (int i=1;i<=n;i++) cin >> s[i] >> v[i];
vi frame(m+1);
for (int i=1;i<=m;i++) cin >> frame[i];
sort(frame.begin()+1,frame.end());
vi pics(n+1);
iota(all(pics),0ll);
sort(pics.begin()+1,pics.end(),[&](int x,int y) {
if (v[x] != v[y]) return v[x] < v[y];
return s[x] < s[y];
});
for (int i=1;i<=n;i++) val[i] = s[pics[i]];
int ans = 0;
int cur = m,allow = n;
ST st(n);
while (cur >= 1 && allow >= 1) {
int frst = st.walk(1,1,n,1,allow,frame[cur]);
if (frst == 0) break;
allow = frst-1;
ans++;
cur--;
}
cout << ans << '\n';
}
int32_t main() {
ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
#ifdef Dodi
freopen("in.txt","r",stdin);
freopen("out.txt","w",stdout);
#endif
int t = 1;
//cin >> t;
while (t --> 0) solve();
}
