/* code by the cute ~~Dengdualang~~ PixelCat owo */
/* as cute as nacho neko (aka. my wife)! */
/* Nhade stay for a night here */
/* 183234 deng deng deng pixelcat oops */
/* (yang wang yesu)*2 */
/* ^ some weird stuff. nvm =w= */
#pragma GCC optimize("O4,unroll-loops,no-stack-protector")
#include <bits/stdc++.h>
#define int LL //__int128
#define double long double
using namespace std;
using LL = long long;
using LLL = __int128_t;
using uLL = unsigned long long;
using pii = pair<int, int>;
#define For(i, a, b) for (int i = a; i <= b; i++)
#define Fors(i, a, b, s) for (int i = a; i <= b; i += s)
#define Forr(i, a, b) for (int i = a; i >= b; i--)
#define F first
#define S second
#define L(id) (id * 2 + 1)
#define R(id) (id * 2 + 2)
#define LO(x) (x & (-x))
#define eb emplace_back
#define all(x) x.begin(), x.end()
#define sz(x) ((int)x.size())
#define mkp make_pair
#define MOD (int)(998244353)
// #define MOD (int)((LL)1e9 + 7)
#define INF (int)(4e18)
// #define INF 1e9
#define EPS (1e-6)
#ifdef NYAOWO
#include "library/debug.hpp"
inline void USACO(const string &s) {
cerr << "USACO: " << s << "\n";
}
#else
#define debug(...)
inline void timer() {}
inline void USACO(const string &s) {
freopen((s + ".in").c_str(), "r", stdin);
freopen((s + ".out").c_str(), "w", stdout);
}
#endif
inline void NYA() {
ios::sync_with_stdio(false);
cin.tie(0);
}
inline int gcd(int a, int b) {
return __gcd(a, b);
}
inline int lcm(int a, int b) {
return a / gcd(a, b) * b;
}
int fpow(int b, int p, const int &mod) {
int ans = 1;
while (p) {
if (p & 1) ans = ans * b % mod;
p >>= 1;
b = b * b % mod;
}
return ans;
}
int fpow(int b, int p) {
return fpow(b, p, MOD);
}
template <typename T>
inline void chmin(T &_a, const T &_b) {
if (_b < _a) _a = _b;
}
template <typename T>
inline void chmax(T &_a, const T &_b) {
if (_b > _a) _a = _b;
}
// mt19937_64 rng(
// chrono::steady_clock::now().time_since_epoch().count());
const int MAXN=210;
int x[MAXN];
int t[MAXN];
int dp[MAXN][MAXN][2][MAXN];
int32_t main() {
NYA();
// nyaacho >/////<
// miku sama bless me >/////<
int n,L; cin>>n>>L;
For(i,1,n) cin>>x[i];
For(i,1,n) cin>>t[i];
x[n+1]=L;
auto dist=[&](int a,int b) -> int{
int owo=(abs(x[a]-x[b]))%L;
return min(owo,L-owo);
};
memset(dp,0x3f3f3f3f,sizeof(dp));
dp[n+1][0][0][0]=dp[n+1][0][1][0]=0;
Forr(l,n+1,2) For(r,0,l-2) For(end,0,1) For(get,0,n){
auto &now=dp[l][r][end][get];
if(now>INF) continue;
int nx;
if(end) nx=r;
else nx=l;
// go to left
int tm=now+dist(nx,l-1);
chmin(dp[l-1][r][0][get+(tm<=t[l-1])],tm);
//go to right
tm=now+dist(nx,r+1);
chmin(dp[l][r+1][1][get+(tm<=t[r+1])],tm);
}
int ans=0;
Forr(l,n+1,1) For(r,0,l-1) For(end,0,1) For(get,0,n){
auto &now=dp[l][r][end][get];
if(now<INF){
chmax(ans,get);
}
}
cout<<ans<<"\n";
// debug(dp[7][0][0][0]);
// debug(dp[6][0][0][1]);
// debug(dp[5][0][0][2]);
// debug(dp[5][1][1][3]);
return 0;
}
