#include <bits/stdc++.h>
#define ff first
#define ss second
#define endl '\n'
using namespace std;
const long long INF = (long long) 1e18;
const int mod = (int) 1e9+7;
const int MAXN = (int) 3e5+5;
typedef long long ll;
typedef unsigned long long ull;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;
ll n, m;
pii pic[MAXN];
int c[MAXN];
int main(){
ios_base::sync_with_stdio(false);
cin.tie(nullptr);cout.tie(nullptr);
#ifdef Local
freopen("C:/Users/Admin/Desktop/Yazilim/C/IO/int.txt","r",stdin);
freopen("C:/Users/Admin/Desktop/Yazilim/C/IO/out.txt","w",stdout);
#endif
cin>>n>>m;
for(int i = 0; i < n; i++){
int v, s;
cin>>s>>v;
pic[i] = {v, s};
}
sort(pic, pic + n);
for(int i = 0; i < m; i++){
cin>>c[i];
}
sort(c, c + m);
ll res = 0, cur = n - 1;
for(int j = m - 1; j >= 0; j--){
while(cur >= 0 && pic[cur].ss > c[j]) cur--;
if(cur >= 0){
cur--;
res++;
}
}
cout<<res<<endl;
#ifdef Local
cout<<endl<<fixed<<setprecision(2)<<1000.0 * clock() / CLOCKS_PER_SEC<< " milliseconds ";
#endif
}
