#include <bits/stdc++.h>
using namespace std;
using ll = long long;
inline void fastio() {
std::ios_base::sync_with_stdio(false);
std::cin.tie(nullptr);
std::cout.tie(nullptr);
}
const ll INF = 0x3f3f3f3f3f3f3f3f;
ll n, l, ans;
ll arr[202], t[202];
ll cdp[202][202][202], rdp[202][202][202]; // 시계, 반시계, 개수
int main() {
fastio();
cin >> n >> l;
for (ll i = 1; i <= n; i++) {
cin >> arr[i];
}
arr[n + 1] = l;
for (ll i = 1; i <= n; i++) {
cin >> t[i];
}
memset(cdp, 0x3f, sizeof(cdp));
memset(rdp, 0x3f, sizeof(rdp));
for (ll i = 0; i <= n; i++) {
for (ll j = n + 1; j > i; j--) {
for (ll k = 0; k <= n; k++) {
if (i == 0 and j == n + 1 and k == 0) {
cdp[i][j][k] = rdp[i][j][k] = 0;
}
ll& x = cdp[i][j][k];
if (i > 0) {
ll ct = arr[i] - arr[i - 1], rt = l - arr[j] + arr[i];
if (k > 0 and cdp[i - 1][j][k - 1] + ct <= t[i]) x = min(x, cdp[i - 1][j][k - 1] + ct);
if (cdp[i - 1][j][k - 1] + ct > t[i]) x = min(x, cdp[i - 1][j][k] + ct);
if (k > 0 and rdp[i - 1][j][k - 1] + rt <= t[i]) x = min(x, rdp[i - 1][j][k - 1] + rt);
if (rdp[i - 1][j][k - 1] + rt > t[i]) x = min(x, rdp[i - 1][j][k] + rt);
}
ll& y = rdp[i][j][k];
if (j <= n) {
ll rt = arr[j + 1] - arr[j], ct = l - arr[j] + arr[i];
if (k > 0 and rdp[i][j + 1][k - 1] + rt <= t[j]) y = min(y, rdp[i][j + 1][k - 1] + rt);
if (rdp[i][j + 1][k - 1] + rt > t[j]) y = min(y, rdp[i][j + 1][k] + rt);
if (k > 0 and cdp[i][j + 1][k - 1] + ct <= t[j]) y = min(y, cdp[i][j + 1][k - 1] + ct);
if (cdp[i][j + 1][k - 1] + ct > t[j]) y = min(y, cdp[i][j + 1][k] + ct);
}
if (ans < k) {
if (x != INF) ans = k;
if (y != INF) ans = k;
}
}
}
}
cout << ans;
return 0;
}
