#include <bits/stdc++.h>
#define ll long long
#define fi first
#define se second
#define sz(x) (int)x.size()
#define ALL(v) v.begin(),v.end()
#define MASK(k) (1LL << (k))
#define BIT(x, i) (((x) >> (i)) & 1)
#define oo (ll)1e18
#define INF (ll)1e9
#define MOD (ll)(998244353)
using namespace std;
template<class T1, class T2>
bool maximize(T1 &a, T2 b){if(a < b){a = b; return true;} return false;}
template<class T1, class T2>
bool minimize(T1 &a, T2 b){if(a > b){a = b; return true;} return false;}
template<class T1, class T2>
void add(T1 &a, T2 b){a += b; if(a >= MOD) a -= MOD;}
template<class T1, class T2>
void sub(T1 &a, T2 b){a -= b; if(a < 0) a += MOD;}
template<class T>
void cps(T &v){sort(ALL(v)); v.resize(unique(ALL(v)) - v.begin());}
const int MAX = 5e5 + 10;
int N, M;
pair<int, int> a[MAX];
int x[MAX], y[MAX];
void solve(){
cin >> N >> M;
for(int i=1; i<=M; i++){
cin >> x[i];
}
for(int i=1; i<=M; i++){
cin >> y[i];
}
for(int i=1; i<=M; i++){
a[i] = make_pair(x[i] - y[i], x[i] + y[i]);
}
sort(a + 1, a + M + 1);
vector<int> lst;
for(int i=1; i<=M; i++){
int p = lower_bound(ALL(lst), -a[i].se) - lst.begin();
if(p == sz(lst)){
lst.push_back(-a[i].se);
}
else{
lst[p] = -a[i].se;
}
}
cout << sz(lst) << '\n';
}
int main(){
ios_base::sync_with_stdio(0); cin.tie(0);
// freopen("split.inp", "r", stdin);
// freopen("split.out", "w", stdout);
int tt = 1;
// cin >> tt;
while(tt--){
solve();
}
return 0;
}
