#include <bits/stdc++.h>
typedef long long ll;
struct Point {
ll x, y;
void transform() {
ll u = y + x, v = y - x;
x = u, y = v;
}
};
int main() {
std::ios_base::sync_with_stdio(false);
std::cin.tie(nullptr);
ll n, m;
std::cin >> n >> m;
std::vector<Point> pts(m + 1);
std::vector<ll> t(m + 1), a(m + 1);
for (ll i = 1; i <= m; ++i) {
std::cin >> t[i];
pts[i].x = t[i];
}
for (ll i = 1; i <= m; ++i) {
std::cin >> a[i];
pts[i].y = a[i];
}
for (auto &i : pts) {
i.transform();
}
std::sort(pts.begin(), pts.end(), [](Point a, Point b) { return a.x < b.x; });
pts[0].x = -1e15, pts[0].y = -1e15;
std::vector<std::vector<ll>> dp(m + 2, std::vector<ll>(m + 2));
for (ll i = m; i >= 1; --i) {
for (ll j = m; j >= 0; --j) {
dp[i][j] = dp[i + 1][j];
if (pts[i].x > pts[j].x and pts[i].y > pts[j].y) {
dp[i][j] = std::max(dp[i][j], dp[i + 1][i] + 1);
}
}
}
std::cout << dp[1][0] << '\n';
}
