#include <bits/stdc++.h>
using namespace std;
int n, l;
vector<int> x, t;
int get() {
int ans = 0;
for (int s = 0; s <= n; s++) {
int res = 0, k = 0;
for (int i = 0; i < s; i++) {
k = x[i];
if (k <= t[i]) {
res++;
}
}
k *= 2;
int prv = l;
for (int i = n - 1; i >= 0; i--) {
k += prv - x[i];
prv = x[i];
if (k <= t[i]) {
res++;
}
}
ans = max(ans, res);
}
return ans;
}
int main() {
ios::sync_with_stdio(false);
cin.tie(nullptr);
cin >> n >> l;
x.resize(n);
t.resize(n);
for (int i = 0; i < n; i++) {
cin >> x[i];
}
for (int i = 0; i < n; i++) {
cin >> t[i];
}
int ans = get();
for (int i = 0; i < n; i++) {
x[i] = l - x[i];
}
ranges::reverse(x);
ranges::reverse(t);
ans = max(ans, get());
cout << ans << '\n';
return 0;
}
