#include <bits/stdc++.h>
#pragma GCC optimize("Ofast,unroll-loops")
#define bupol __builtin_popcount
#define int long long
#define ll long long
#define ld long double
#define fi first
#define se second
#define pb push_back
#define lf (id<<1)
#define rg ((id<<1)|1)
#define md ((l+r)>>1)
using namespace std;
const int MAXN = 2e5+5;
const int MAXK = 205;
const int LOG = 20;
const int MOD = 1e9+7;
const int SQRT = 520;
const int INF = 1e18+10;
const int INF2 = 1e18;
typedef pair<ll,ll> pii;
typedef pair<ll,pii> ipii;
bool cmp(pii a, pii b){
if(a.fi==b.fi) return a.se > b.se;
return a.fi > b.fi;
}
int n, m;
vector <int> x;
vector <pii> val;
bool cek(int p){
int idx = 1, i=1, cnt = 0;
for(i=1; i<=p; i++){
while(idx<=n && val[idx].se > x[i]){
idx++;
continue; // lebih gede
}
//if(p==2) cout << idx << " idx\n";
if(idx<=n && val[idx].se <= x[i]){
cnt++; idx++;
}
}
if(cnt == p) return 1;
return 0;
}
void bin(){
int l=1, r=min(n, m), ans = 0;
while(l<=r){
int mid = ((l+r)>>1);
if(cek(mid)){
ans = mid;
l = mid+1;
} else {
r = mid-1;
}
}
cout << ans << '\n';
}
signed main(){
ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
cin >> n >> m;
for(int i=1; i<=n; i++){
int a, b; cin >> a >> b;
val.pb({b, a});
}
val.pb({INF, INF});
sort(val.begin(), val.end(), cmp);
for(int i=1; i<=m; i++){
int pp; cin >> pp; x.pb(pp);
}
sort(x.begin(), x.end()); x.pb(-1);
reverse(x.begin(), x.end());
// for(auto in : val) cout << in.fi << ' '<< in.se << " in\n";
// for(auto in : x) cout << in << " pp\n";
bin();
}
