#include <bits/stdc++.h>
using namespace std;
using ll = long long;
const int N = 200 + 24;
const ll INF = 1e18;
int n; ll L;
ll x[N], t[N];
pair<ll, ll> dp[N][N][2];
ll dist(ll px, ll py) {
return min(L - px + py, abs(px - py));
}
void solve() {
cin >> n >> L;
for (int i = 1; i <= n; i++) cin >> x[i];
for (int i = 1; i <= n; i++) cin >> t[i];
x[0] = L, t[0] = INF;
x[n + 1] = L, t[n + 1] = INF;
for (int i = 0; i <= n + 1; i++) {
for (int j = 0; j <= n + 1; j++) {
dp[i][j][0] = dp[i][j][1] = {0, INF};
}
}
dp[0][n + 1][0] = dp[0][n + 1][1] = {0, 0};
for (int i = 0; i <= n + 1; i++) {
for (int j = n + 1; j >= i + 2; j--) {
for (int p = 0; p <= 1; p++) {
ll cnt = dp[i][j][p].first, min_time = dp[i][j][p].second;
if (min_time > INF) continue;
ll new_cnt, new_min_time;
new_min_time = min_time + dist(x[(p == 0 ? i : j)], x[j - 1]);
new_cnt = cnt + (new_min_time <= t[j - 1]);
dp[i][j - 1][1] = max(dp[i][j][p], {new_cnt, new_min_time});
new_min_time = min_time + dist(x[(p == 0 ? i : j)], x[i + 1]);
new_cnt = cnt + (new_min_time <= t[i + 1]);
dp[i + 1][j][0] = max(dp[i + 1][j][0], {new_cnt, new_min_time});
}
}
}
ll res = 0;
for (int i = 0; i <= n + 1; i++) {
for (int j = j + 1; j <= n + 1; j++) {
for (int p = 0; p <= 1; p++) {
// cout << i << ' ' << j << ' ' << p << ' ' << dp[i][j][p].first << ' ' << dp[i][j][p].second << '\n';
res = max(res, dp[i][j][p].first);
}
}
}
cout << res << '\n';
}
int main() {
cin.tie(0) -> sync_with_stdio(0);
int T = 1; // cin >> T;
while (T--) {
solve();
}
}
