#include <bits/stdc++.h>
using namespace std;
using ll = long long;
ll INF = 1e18;
int main() {
ios::sync_with_stdio(false);
cin.tie(nullptr);
cout.tie(nullptr);
ll n, dist;
cin >> n >> dist;
vector<ll> s(n), z(n);
ll las = 0;
for (ll i = 0; i < n; i++) {
cin >> s[i];
las = s[i];
}
vector<ll> v2(n);
v2[0] = dist - las;
for (ll i = 1; i < n; i++) {
v2[i] = s[n - i] - s[n - i - 1];
}
for (ll i = n - 1; i >= 1; i--) {
s[i] = s[i] - s[i - 1];
}
for (ll i = 0; i < n; i++) {
cin >> z[i];
}
auto v1 = s;
vector<ll> sum_l(n + 1);
vector<ll> sum_r(n + 1);
vector<ll> time_l(n);
vector<ll> time_r(n);
for (ll i = 0; i < n; i++) {
sum_l[i + 1] = sum_l[i] + v1[i];
}
for (ll i = 0; i < n; i++) {
time_l[i] = z[i];
}
time_r = time_l;
reverse(time_r.begin(), time_r.end());
for (ll i = 0; i < n; i++) {
sum_r[i + 1] = sum_r[i] + v2[i];
}
vector<vector<vector<vector<ll>>>> dp(n + 1, vector<vector<vector<ll>>>(n + 1, vector<vector<ll>>(n + 1,
vector<ll>(2,
INF))));
dp[0][0][0][0] = 0;
dp[0][0][0][1] = 0;
ll ans = 0;
for (ll i = 0; i < n; i++) {
for (ll j = 0; j <= i; j++) {
for (ll e = 0; e <= i; e++) {
ll l = j;
ll r = i - j;
ll tm = dp[l][r][e][0];
ll all = sum_l[l] + sum_r[r];
dp[l + 1][r][e][0] = min(dp[l + 1][r][e][0], tm + v1[l]);
if (tm + v1[l] <= time_l[l]) {
dp[l + 1][r][e + 1][0] = min(dp[l + 1][r][e + 1][0], tm + v1[l]);
}
dp[l + 1][r][e][1] = min(dp[l + 1][r][e][1], tm + v1[l] + v1[l] + all);
if (tm + v1[l] <= time_l[l]) {
dp[l + 1][r][e + 1][1] = min(dp[l + 1][r][e + 1][1], tm + v1[l] + v1[l] + all);
}
tm = dp[l][r][e][1];
dp[l][r + 1][e][1] = min(dp[l][r + 1][e][1], tm + v2[r]);
if (tm + v2[r] <= time_r[r]) {
dp[l][r + 1][e + 1][1] = min(dp[l][r + 1][e + 1][1], tm + v2[r]);
}
dp[l][r + 1][e][0] = min(dp[l][r + 1][e][0], tm + v2[r] + v2[r] + all);
if (tm + v2[r] <= time_r[r]) {
dp[l][r + 1][e + 1][0] = min(dp[l][r + 1][e + 1][0], tm + v2[r] + v2[r] + all);
}
}
}
}
for (ll i = 0; i <= n; i++) {
for (ll j = 0; j <= i; j++) {
for (ll e = 0; e <= i; e++) {
ll l = j;
ll r = i - j;
if (dp[l][r][e][0] < INF) {
ans = max(ans, e);
}
if (dp[l][r][e][1] < INF) {
ans = max(ans, e);
}
}
}
}
cout << ans;
}
