#include<bits/stdc++.h>
#define f first
#define s second
#define ll long long
using namespace std;
int n , m;
pair<ll , ll> p[100005];
ll fr[100005];
int main (){
ios_base::sync_with_stdio(0);
cin.tie(0);
cin >> n >> m;
for(int i = 0; i < n; ++i) cin >> p[i].s >> p[i].f;
for(int i = 0; i < m; ++i) cin >> fr[i];
sort(p , p + n); sort(fr, fr + m);
int ans = 0;
// cerr << p[n - 1].s << endl;
for(int i = n - 1; i >=0; --i){
//cerr << fr[m - ans - 1] << " fi " << endl;
//cerr << p[i].s << " pis " << endl;
if(fr[m - ans - 1] >= p[i].s){ ++ans; if(ans == m) break;}
}cout << ans << endl;
}
