#include <bits/stdc++.h>
#define pb push_back
#define ll long long int
#define all(v) (v).begin(),(v).end()
#define fi first
#define se second
using namespace std;
int main() {
ll n, l, mx = 0; cin >> n >> l;
vector<ll> x(n), t(n);
for (int i = 0; i < n; i++) cin >> x[i];
for (int i = 0; i < n; i++) cin >> t[i];
// clockwise
ll cur = 0;
for (int i = 0; i < n; i++) {
if (t[i] < x[i]) cur++;
}
mx = max(mx, n-cur);
// anticlockwise
cur = 0;
for (int i = n-1; i >= 0; i--) {
if (t[i] < l-x[i]) cur++;
}
mx = max(mx, n-cur);
cur = 0;
for (int i = 0; i < n; i++) {
if (t[i] < x[i]) cur++; ll curr = 0;
for (int j = n-1; j > i; j--) {
if (t[j] < 2*x[i]+(l-x[j])) curr++;
mx = max(mx, n-(j-i)+1-cur-curr);
}
}
cur = 0;
for (int i = n-1; i >= 0; i--) {
if (t[i] < l-x[i]) cur++; ll curr = 0;
for (int j = 0; j < i; j++) {
if (t[j] < 2*(l-x[i])+x[j]) curr++;
mx = max(mx, n-(i-j)+1-cur-curr);
}
}
cout << mx;
return 0;
}
