#include <iostream>
#include <vector>
#include <algorithm>
#include <set>
#define rep(i, s, e) for (ll i = s; i < e; i++)
#define upmin(a, b) a = min(a, b)
#define upmax(a, b) a = max(a, b)
using namespace std;
using ll = long long;
using vll = vector<ll>;
using pll = pair<ll, ll>;
using vpll = vector<pll>;
void solve() {
ll n, m;
cin >> n >> m;
vpll arr(m);
rep(i, 0, m) cin >> arr[i].second;
rep(i, 0, m) cin >> arr[i].first;
sort(arr.begin(), arr.end());
vll dp(m);
dp[0] = 1;
ll l = 0;
multiset<pll> s;
s.insert({ arr[0].second, arr[0].first });
rep(i, 1, m) {
pll cur = { arr[i].second, arr[i].first };
s.insert(cur);
/*cout << "s: " << '\n';
for (auto& it : s) {
cout << it.first << ' ' << it.second << '\n';
}*/
while (!s.empty() && l < i){
bool updated = false;
if (*(--s.end()) != cur) {
auto itR = ++(s.find(cur));
ll a1 = arr[i].first;
ll a2 = (*itR).second;
ll t1 = arr[i].second;
ll t2 = (*itR).first;
if (abs(a1 - a2) > abs(t2 - t1)) {
// Won't make it in time
s.erase({ arr[l].second, arr[l].first });
l++;
updated = true;
}
}
if (!s.empty() && (*s.begin() != cur)) {
auto itL = --(s.find(cur));
ll a1 = arr[i].first;
ll a2 = (*itL).second;
ll t1 = arr[i].second;
ll t2 = (*itL).first;
if ((abs(a1 - a2) > abs(t1 - t2)) && !updated) {
// Won't make it in time
s.erase({ arr[l].second, arr[l].first });
l++;
updated = true;
}
}
if (!updated) break;
}
if (l > 0) dp[i] = dp[l - 1] + 1;
else dp[i] = 1;
}
/*cout << "dp: ";
rep(i, 0, m) cout << dp[i] << ' ';
cout << '\n';*/
cout << dp[m - 1] << '\n';
}
int main() {
ios_base::sync_with_stdio(false);
cin.tie(0);
solve();
}
