#include <bits/stdc++.h>
#pragma GCC optimize("O3")
using namespace std;
using ll = long long;
#define int ll
signed main() {
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
int n,m; cin >> n >> m;
vector<int> t(m); for(int& i : t) cin >> i;
vector<int> a(m); for(int& i : a) cin >> i;
vector<int> u(m); for(int i = 0; i < m; i++) u[i] = a[i]+t[i];
vector<int> v(m); for(int i = 0; i < m; i++) v[i] = a[i]-t[i];
vector<pair<int,int>> seq(m); for(int i = 0; i < m; i++) seq[i] = {u[i],v[i]};
sort(seq.begin(),seq.end(),[](const pair<int,int>& a, const pair<int,int>& b) -> bool {
return (a.first==b.first)? a.second > b.second : a.first < b.first;
});
vector<int> lis;
for(auto& [u,mv] : seq) {
auto itr = lower_bound(lis.begin(),lis.end(),mv);
if(itr==lis.end()) lis.push_back(mv);
else *itr = mv;
}
cout << lis.size() << "\n";
return 0;
}
