#include<iostream>
#include<vector>
#include<algorithm>
#include<set>
#include<map>
using namespace std;
#define ll long long
#define endl "\n"
#define mp make_pair
#define out(x) cout<< #x << " = " << x << endl
#define pii pair<int,int>
#pragma GCC optimize("Ofast")
int n,m;
pii paint[1004];
int frame[1004];
int dp[1004][1004];
bool comp(pii a,pii b){
if (a.second != b.second) return a.second < b.second;
return a.first < b.first;
}
signed main(){
ios::sync_with_stdio(false); cin.tie(0);
cin>>n>>m;
for (int i=1;i<=n;i++){
cin>>paint[i].first>>paint[i].second;
}
for (int i=1;i<=m;i++) cin>>frame[i];
sort(frame+1,frame+1+m);
sort(paint+1,paint+1+n,comp);
for (int i=1;i<=n;i++) for (int j=1;j<=m;j++){
if (paint[i].first <= frame[j]) dp[i][j] = dp[i-1][j-1] + 1;
dp[i][j] = max(dp[i][j], max(dp[i-1][j], dp[i][j-1]));
}
cout<<dp[n][m]<<endl;
}
