// File stamps3.cpp created on 01.10.2025 at 09:22:52
#include <bits/stdc++.h>
using i64 = long long;
#ifdef DEBUG
#include "/home/ahmetalp/Desktop/Workplace/debug.h"
#else
#define debug(...) void(23)
#endif
constexpr i64 inf = i64(1E18);
template<typename T>
bool chmin(T& a, T b) {
if (a > b) {
a = b;
return true;
}
return false;
}
int main() {
std::ios::sync_with_stdio(false);
std::cin.tie(nullptr);
int N, L;
std::cin >> N >> L;
std::vector<int> X(N), T(N);
for (int i = 0; i < N; ++i) {
std::cin >> X[i];
}
for (int i = 0; i < N; ++i) {
std::cin >> T[i];
}
auto dist = [&](int a, int b) -> i64 {
if (a > b) {
std::swap(a, b);
}
return std::min(b - a, L - b + a);
};
std::vector f(N, std::vector(N, std::vector(N + 1, std::vector<i64>(2, inf))));
for (int i = 0; i < N; ++i) {
chmin(f[i][i][0][0], dist(0, X[i]));
chmin(f[i][i][0][1], dist(0, X[i]));
if (dist(0, X[i]) <= T[i]) {
chmin(f[i][i][1][0], dist(0, X[i]));
chmin(f[i][i][1][1], dist(0, X[i]));
}
}
for (int len = 1; len <= N - 1; ++len) {
for (int l = 0; l < N; ++l) {
int r = (l + len - 1) % N;
for (int t = 0; t <= N; ++t) {
int nl = (N + l - 1) % N;
int nr = (r + 1) % N;
if (f[l][r][t][0] != inf) {
chmin(f[nl][r][t][0], f[l][r][t][0] + dist(X[l], X[nl]));
if (f[l][r][t][0] + dist(X[l], X[nl]) <= T[nl]) {
chmin(f[nl][r][t + 1][0], f[l][r][t][0] + dist(X[l], X[nl]));
}
chmin(f[l][nr][t][0], f[l][r][t][0] + dist(X[l], X[l]));
chmin(f[l][nr][t][1], f[l][r][t][0] + dist(X[l], X[nr]));
if (f[l][r][t][0] + dist(X[l], X[nr]) <= T[nr]) {
chmin(f[l][nr][t + 1][1], f[l][r][t][0] + dist(X[l], X[nr]));
}
}
if (f[l][r][t][1] != inf) {
chmin(f[nl][r][t][0], f[l][r][t][1] + dist(X[r], X[nl]));
if (f[l][r][t][1] + dist(X[r], X[nl]) <= T[nl]) {
chmin(f[nl][r][t + 1][0], f[l][r][t][1] + dist(X[r], X[nl]));
}
chmin(f[nl][r][t][1], f[l][r][t][1] + dist(X[r], X[r]));
chmin(f[l][nr][t][1], f[l][r][t][1] + dist(X[r], X[nr]));
if (f[l][r][t][1] + dist(X[r], X[nr]) <= T[nr]) {
chmin(f[l][nr][t + 1][1], f[l][r][t][1] + dist(X[r], X[nr]));
}
}
}
}
}
int ans = 0;
for (int l = 0; l < N; ++l) {
int r = (l + N - 1) % N;
for (int t = 0; t <= N; ++t) {
if (f[l][r][t][0] != inf) {
ans = std::max(ans, t);
}
if (f[l][r][t][1] != inf) {
ans = std::max(ans, t);
}
}
}
std::cout << ans << '\n';
return 0;
}
