// #pragma optimize ("g",on)
// #pragma GCC optimize ("inline")
// #pragma GCC optimize ("Ofast")
// #pragma GCC optimize ("unroll-loops")
// #pragma GCC optimize ("03")
#include <bits/stdc++.h>
#define pb push_back
#define SS ios_base::sync_with_stdio(0);cin.tie(nullptr);cout.tie(nullptr);
#define int long long
#define all(v) v.begin(),v.end()
using namespace std;
mt19937 rnd(chrono::steady_clock::now().time_since_epoch().count());
const int N = 5e5 + 1, inf = 1e9, mod = 998244353;
void solve(){
int n, l;
cin >> n >> l;
int x[n + 2] = {}, t[n + 2], y[n + 2] = {};
y[n + 1] = l;
x[n + 1] = l;
for(int i = 1; i <= n; i++){
cin >> x[i];
y[n - i + 1] = (l - x[i]);
}
for(int i = 1; i <= n; i++){
cin >> t[i];
}
int dp[n + 2][n + 2][n + 2][2] = {};
for(int i = 0; i <= n; i++){
for(int j = 0; j <= n; j++){
for(int k = 0; k <= n; k++){
for(int d = 0; d < 2; d++) dp[i][j][k][d] = inf;
}
}
}
dp[0][0][0][0] = dp[0][0][0][1] = 0;
for(int i = 0; i <= n; i++){
for(int j = 0; j <= n; j++){
if((i == 0 && j == 0) || i >= n - j + 1) continue;
for(int k = 0; k <= n; k++){
if(k > i + j) break;
if(i > 0) dp[i][j][k][0] = min({dp[i][j][k][0], dp[i - 1][j][k][0] + min(x[i] - x[i - 1], x[i - 1] + y[n - i + 1]), dp[i - 1][j][k][1] + min(x[n - j + 1] - x[i], y[j] + x[i])});
if(j > 0) dp[i][j][k][1] = min({dp[i][j][k][1], dp[i][j - 1][k][1] + min(y[j] - y[j - 1], y[j - 1] + x[n - j + 1]), dp[i][j - 1][k][0] + min(x[n - j + 1] - x[i], x[i] + y[j])});
dp[i][j][k][1] = min(dp[i][j][k][0] + min(x[n - j + 1] - x[i], x[i] + y[j]), dp[i][j][k][1]);
dp[i][j][k][0] = min(dp[i][j][k][1] + min(x[n - j + 1] - x[i], y[j] + x[i]), dp[i][j][k][0]);
if(k > 0){
int dist = inf;
if(j > 0){
dist = min(dp[i][j - 1][k - 1][1] + min(y[j] - y[j - 1], y[j - 1] + x[n - j + 1]), dp[i][j - 1][k - 1][0] + min(x[n - j + 1] - x[i], x[i] + y[j]));
if(dist <= t[n - j + 1]) dp[i][j][k][1] = min(dp[i][j][k][1], dist);
}
if(i > 0){
dist = min(dp[i - 1][j][k - 1][0] + min(x[i] - x[i - 1], x[i - 1] + y[n - i + 1]), dp[i - 1][j][k - 1][1] + min(x[n - j + 1] - x[i], y[j] + x[i]));
if(dist <= t[i]) dp[i][j][k][0] = min(dp[i][j][k][0], dist);
}
}
}
}
}
int ans = 0;
for(int i = 0; i <= n; i++){
for(int j = 0; j <= n; j++){
for(int k = 1; k <= n; k++){
if(dp[i][j][k][0] < inf || dp[i][j][k][1] < inf){
ans = max(ans, k);
}
}
}
}
cout << ans;
}
signed main(){
SS
// freopen("trains.in", "r", stdin);
// freopen("trains.out", "w", stdout);
int t = 1;
// cin >> t;
while(t--){
solve();
}
}
