/*
Author: Nguyen Chi Thanh - High School for the Gifted - VNU.HCM (i2528)
*/
#include <bits/stdc++.h>
using namespace std;
/* START OF TEMPALTE */
// #define int long long
#define ll long long
#define ull unsigned long long
#define ld long double
#define pii pair<int, int>
#define pll pair<ll, ll>
#define fi first
#define se second
#define __builtin_popcount __builtin_popcountll
#define all(x) (x).begin(), (x).end()
#define BIT(x, i) (((x) >> (i)) & 1)
#define MASK(x) (1ll << (x))
#define SZ(a) ((int32_t)a.size())
#define debug(a, l, r) {for (int _i = (l); _i <= (r); ++_i) cout << (a)[_i] << ' '; cout << '\n';}
template<class X, class Y>
bool minimize(X &x, const Y &y) {
if (x > y) {
x = y;
return true;
} else return false;
}
template<class X, class Y>
bool maximize(X &x, const Y &y) {
if (x < y) {
x = y;
return true;
} else return false;
}
/* END OF TEMPALTE */
const int MAXN = 5e5 + 5;
int n, m, a[MAXN], dp[MAXN];
pii info[MAXN];
struct Normalize{
vector<int> vals;
void add(int x) {
vals.push_back(x);
}
void build() {
sort(all(vals));
vals.erase(unique(all(vals)), end(vals));
}
int get(int x) {
return (int)(lower_bound(all(vals), x) - begin(vals)) + 1;
}
};
struct FenwickTree {
int n;
vector<int> fen;
FenwickTree() {
}
void init(int _n) {
n = _n;
fen.resize(n + 5, 0);
}
void update(int idx, int v) {
for (int i = idx; i <= n; i += i & -i)
maximize(fen[i], v);
}
int get(int idx) {
int res = 0;
for (int i = idx; i; i -= i & -i)
maximize(res, fen[i]);
return res;
}
};
void init() {
cin >> n >> m;
for (int i = 1; i <= m; ++i) cin >> info[i].fi;
for (int i = 1; i <= m; ++i) cin >> info[i].se;
for (int i = 1; i <= m; ++i)
info[i] = {info[i].fi + info[i].se, info[i].fi - info[i].se};
sort(info + 1, info + m + 1);
Normalize norm;
for (int i = 1; i <= m; ++i)
norm.add(-info[i].se);
norm.build();
for (int i = 1; i <= m; ++i)
a[i] = norm.get(-info[i].se);
}
void solve() {
FenwickTree fen;
fen.init(m);
for (int i = 1; i <= m; ++i) {
dp[i] = 1 + fen.get(a[i] - 1);
fen.update(a[i], dp[i]);
}
cout << *max_element(dp + 1, dp + m + 1);
}
signed main() {
#ifdef NCTHANH
freopen("input.txt", "r", stdin);
freopen("output.txt", "w", stdout);
#endif
ios_base::sync_with_stdio(0);
cin.tie(nullptr); cout.tie(nullptr);
init();
solve();
return 0;
}
