#include<bits/stdc++.h>
#include<ext/pb_ds/assoc_container.hpp>
/**zagaro & lauren <3**/
#define mod 1000000007 //1e9 + 7
#define pi acos(-1)
#define wl while
#define str string
#define ENDL "\n"
#define sal ' '
#define tp_set ll
#define prc(n) cout.precision(n);cout<<fixed;
#define ord_set tree<tp_set, null_type, less<tp_set>, rb_tree_tag, tree_order_statistics_node_update>
typedef long long ll;
typedef bool bl;
typedef char car;
using namespace std;
using namespace __gnu_pbds;
vector<ll> tr;
vector<ll> frm;
void build(ll ind, ll l, ll r){
if(l == r){tr[ind] = frm[l];return ;}
build(ind*2, l, (l+r)/2);
build(ind*2+1, (l+r)/2+1, r);
tr[ind] = max(tr[ind*2], tr[ind*2+1]);
return ;
}
ll query(ll ind, ll l, ll r, ll x, ll y, ll v){
if(y < l || r < x)return LONG_LONG_MAX;
if(tr[ind] < v)return LONG_LONG_MAX;
if(l == r && tr[ind] >= v)return l;
ll a;
a = query(ind*2, l, (l+r)/2, x, y, v);
if(a != LONG_LONG_MAX)return a;
else return query(ind*2+1, (l+r)/2+1, r, x, y, v);
}
int main(){
ios_base::sync_with_stdio(0);
cin.tie(0); cout.tie(0);
ll n, m, l, r, M, x;
cin>>n>>m;
vector<pair<ll,ll> > vec(n+1);
frm.assign(m+1, 0);
tr.assign(3*m+10, 0);
vector<ll> dp(1, 0);
vector<ll> ps(1, 0);
for(int i=1;i<=n;i++)cin>>vec[i].first>>vec[i].second;
sort(vec.begin(), vec.end());
for(int i=1;i<=m;i++)cin>>frm[i];
sort(frm.begin(), frm.end());
build(1, 1, m);
for(int i=1;i<=n;i++){
l=0;r=dp.size();
wl(l<r-1){
M = (l+r)/2;
if(dp[M] <= vec[i].second)l=M;
else r=M;
}
x = query(1, 1, m, ps[l]+1, m, vec[i].first);
if(x != LONG_LONG_MAX){
if(l == dp.size()-1){
dp.push_back(vec[i].second);
ps.push_back(x);
}
else {
dp[r] = vec[i].second;
ps[r] = x;
}
}
}
cout<<dp.size()-1<<ENDL;
return 0;
}
