#include <bits/stdc++.h>
using namespace std;
#define int long long
const int MAXN = 205;
const long long INF = 1e18;
int n, L;
vector<int> X(MAXN), T(MAXN);
// distância do ponto inicial (0) até um stamp i
int start_dist(int i) {
return min(X[i], L - X[i]);
}
int32_t main() {
ios::sync_with_stdio(false);
cin.tie(NULL);
cin >> n >> L;
for (int i = 1; i <= n; i++) cin >> X[i];
for (int i = 1; i <= n; i++) cin >> T[i];
// dp[l][r][side] = tempo mínimo para visitar [l..r]
// side = 0 → termina em l
// side = 1 → termina em r
static long long dp[MAXN][MAXN][2];
for (int l = 1; l <= n; l++)
for (int r = 1; r <= n; r++)
dp[l][r][0] = dp[l][r][1] = INF;
int ans = 0;
// casos base: intervalos unitários
for (int i = 1; i <= n; i++) {
// indo direto (clockwise)
if (X[i] <= T[i]) {
dp[i][i][0] = min(dp[i][i][0], (long long)X[i]);
dp[i][i][1] = min(dp[i][i][1], (long long)X[i]);
ans = max(ans, 1LL);
}
// indo pelo outro lado (counter-clockwise)
if (L - X[i] <= T[i]) {
dp[i][i][0] = min(dp[i][i][0], (long long)(L - X[i]));
dp[i][i][1] = min(dp[i][i][1], (long long)(L - X[i]));
ans = max(ans, 1LL);
}
}
// expandindo intervalos
for (int len = 2; len <= n; len++) {
for (int l = 1; l + len - 1 <= n; l++) {
int r = l + len - 1;
// termina em l
// vindo de l+1 → l
if (dp[l+1][r][0] < INF) {
long long time = dp[l+1][r][0] + (X[l+1] - X[l]);
if (time <= T[l]) dp[l][r][0] = min(dp[l][r][0], time);
}
// vindo de r → l
if (dp[l+1][r][1] < INF) {
long long time = dp[l+1][r][1] + (X[r] - X[l]);
if (time <= T[l]) dp[l][r][0] = min(dp[l][r][0], time);
}
// termina em r
// vindo de r-1 → r
if (dp[l][r-1][1] < INF) {
long long time = dp[l][r-1][1] + (X[r] - X[r-1]);
if (time <= T[r]) dp[l][r][1] = min(dp[l][r][1], time);
}
// vindo de l → r
if (dp[l][r-1][0] < INF) {
long long time = dp[l][r-1][0] + (X[r] - X[l]);
if (time <= T[r]) dp[l][r][1] = min(dp[l][r][1], time);
}
if (dp[l][r][0] < INF || dp[l][r][1] < INF)
ans = max(ans, (int)(r - l + 1));
}
}
cout << ans << "\n";
return 0;
}
