#include <bits/stdc++.h>
#define F first
#define S second
using namespace std;
using ll = long long;
using pi = pair<int, int>;
using vi = vector<int>;
template<class T> bool ckmin(T& a, T b) { return b < a ? a = b, true : false; }
template<class T> bool ckmax(T& a, T b) { return a < b ? a = b, true : false; }
const int N = 2e2+7;
int n, L, x[N], t[N];
ll dp[N][N][N][2];
bool can(int a, ll t, int b, ll te, bool around = 0) {
int d = (around == 0 ? abs(a - b) : L - abs(a - b));
return te + d <= t;
}
int main() {
ios::sync_with_stdio(0); cin.tie(0);
cin >> n >> L;
for (int i = 1; i <= n; ++i) cin >> x[i];
for (int i = 1; i <= n; ++i) cin >> t[i];
x[n+1]=L;
for (int i = 0; i <= n; ++i) {
for (int j = 0; j <= n; ++j) {
for (int cnt = 0; cnt <= n; ++cnt) {
dp[i][j][cnt][0] = 1e18;
dp[i][j][cnt][1] = 1e18;
}
}
}
dp[0][0][0][0] = dp[0][0][0][1] = 0;
for (int i = 0; i <= n; ++i) {
for (int j = 0; i + j <= n; ++j) {
for (int cnt = 0; cnt <= i + j; ++cnt) {
ckmin(dp[i+1][j][cnt][0], dp[i][j][cnt][0]+x[i+1]-x[i]);
ckmin(dp[i][j+1][cnt][1], dp[i][j][cnt][1]+x[n-j+1]-x[n-j]);
if (can(x[i+1], t[i+1], x[i], dp[i][j][cnt][0], 0)) ckmin(dp[i+1][j][cnt+1][0], dp[i][j][cnt][0]+x[i+1]-x[i]);
if (can(x[i+1], t[i+1], x[n-j+1], dp[i][j][cnt][1], 1)) ckmin(dp[i+1][j][cnt+1][0], dp[i][j][cnt][1]+x[i+1]+L-x[n-j+1]);
if (can(x[n-j], t[n-j], x[n-j+1], dp[i][j][cnt][1], 0)) ckmin(dp[i][j+1][cnt+1][1], dp[i][j][cnt][1]+x[n-j+1]-x[n-j]);
if (can(x[n-j], t[n-j], x[i], dp[i][j][cnt][0], 1)) ckmin(dp[i][j+1][cnt+1][1], dp[i][j][cnt][0]+x[i]+L-x[n-j]);
}
}
}
int ans = 0;
for (int i = 0; i <= n; ++i) {
for (int j = 0; i+j <= n; ++j) {
for (int cnt = 0; cnt <= n; ++cnt) {
if (dp[i][j][cnt][0] != 1e18) ckmax(ans, cnt);
if (dp[i][j][cnt][1] != 1e18) ckmax(ans, cnt);
}
}
}
cout << ans << "\n";
}
