#include <bits/stdc++.h>
#define ll long long
using namespace std;
int main()
{
ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
int N,M; cin >> N >> M;
vector<pair<ll,ll>> art(N+1);
for(int i = 1;i<=N;++i) cin >> art[i].second >> art[i].first;
sort(art.begin(),art.end());
vector<ll> frames(M+1);
for(int i = 1;i<=M;++i) cin >> frames[i];
sort(frames.begin(),frames.end());
int j = N, ans = 0;
for(int i = M;i>=1;--i){
while(j > 0 && art[j].second > frames[i]) j--;
if(j > 0){
ans++;
--j;
}
}
cout << ans << "\n";
return 0;
}
