// Success consists of going from failure to failure without loss of enthusiasm
#include <bits/stdc++.h>
using namespace std;
#define nl '\n'
#define sz(x) int(x.size())
template<class T> using V = vector<T>;
const int INF = 1e9+10;
int main() {
cin.tie(0)->sync_with_stdio(0);
int N, L; cin >> N >> L;
V<int> A(N), T(N);
for(auto& x : A) cin >> x;
for(auto& x : T) cin >> x;
A.insert(begin(A), 0); T.insert(begin(T), -1);
A.push_back(0); T.push_back(-1);
// for(auto& x : A) cout << x << " ";
// cout << endl;
// for(auto& x : T) cout << x << " ";
// cout << endl;
// dp[SFX][PFX][K][2] = min time
int dp[N + 1][N + 1][N + 1][2];
for(int i = 0; i <= N; i++) for(int j = 0; j <= N; j++) {
for(int k = 0; k <= N; k++) for(int l = 0; l < 2; l++) {
dp[i][j][k][l] = INF;
}
}
int ans = 0;
dp[0][0][0][0] = 0;
for(int w = 0; w <= N; w++) {
for(int s = 0; s <= N; s++) {
int p = w - s; if (p < 0) continue;
for(int k = 0; k <= N; k++) for(int x = 0; x < 2; x++) if (dp[s][p][k][x] != INF) {
// cout << s << " " << p << " " << k << " " << x << " -> " << dp[s][p][k][x] << endl;
ans = max(ans, k);
int i = (x == 0 ? sz(A) - 1 - s : p);
if (w+1 <= N) {
// move left
{
int ni = (sz(A) - 1 - s - 1);
int nt = dp[s][p][k][x] + min(L - abs(A[i] - A[ni]), abs(A[i] - A[ni]));
// cout << "LEFT: " << nt << endl;
int get = (T[ni] >= nt);
dp[s+1][p][k + get][0] = min(dp[s+1][p][k + get][0], nt);
}
// move right
{
int ni = p + 1;
int nt = dp[s][p][k][x] + min(L - abs(A[i] - A[ni]), abs(A[i] - A[ni]));
// cout << "RIGHT: " << nt << endl;
int get = (T[ni] >= nt);
dp[s][p+1][k + get][1] = min(dp[s][i+1][k + get][1], nt);
}
}
}
}
}
cout << ans << nl;
return 0;
}
