#define NDEBUG
#ifdef NDEBUG
#define dbg(TXTMSG) if constexpr (false) cerr << "lol"
#define dbgv(VARN) ((void)0)
#define dbgfor(COND) if constexpr (false) for (COND)
#else
#define _GLIBCXX_DEBUG 1
#define _GLIBCXX_DEBUG_PEDANTIC 1
#pragma GCC optimize("trapv")
#define dbg(TXTMSG) cerr << "\n" << TXTMSG
#define dbgv(VARN) cerr << "\n" << #VARN << " = "<< VARN << ", line " << __LINE__ << "\n"
#define dbgfor(COND) for (COND)
#endif
#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using pll = pair<ll,ll>;
#define e0 first
#define e1 second
constexpr ll INFTY = 1e18;
int main()
{
ll N,L;
cin >> N >> L;
vector<ll> X(N+2);
vector<ll> T(N+2);
X[0] = 0;
X[N+1] = L;
for (ll i = 0; i < N; ++i)
{
cin >> X[i+1];
}
T[0] = -1;
T[N+1] = -1;
for (ll i = 0; i < N; ++i)
{
cin >> T[i+1];
}
// dp[ccw limit][cw limit][num] = {time_ccw, time_cw};
vector<vector<vector<pll>>> dp(N+1,vector<vector<pll>>(N+1,vector<pll>(N+1,{INFTY,INFTY})));
dp[0][0][0]={0,0};
for (ll ns=1;ns<=N; ++ns)
{
dp[0][0][ns] = {INFTY,INFTY};
}
for (ll ccw = 0; ccw <= N; ++ccw)
{
for (ll cw = 0; cw <= N; ++cw)
{
if (cw+ccw>=N) continue;
dbgv(ccw << " " << cw);
for (ll ns = 0; ns < N; ++ns)
{
//dbgv(ns);
// cw entend
if (dp[ccw][cw][ns].e1<INFTY)
{
bool cancollect = T[cw]>=dp[ccw][cw][ns].e1;
//assert(!cancollect);
dp[ccw][cw+1][ns+cancollect].e1 = min(dp[ccw][cw+1][ns+cancollect].e1, (X[cw+1]-X[cw]) + dp[ccw][cw][ns].e1);
dp[ccw+1][cw][ns+cancollect].e0 = min(dp[ccw+1][cw][ns+cancollect].e0, X[cw]+(L-X[N+1-(ccw+1)]) + dp[ccw][cw][ns].e1);
}
//dbgv(ns);
// ccw extend
if (dp[ccw][cw][ns].e0 < INFTY)
{
bool cancollect = T[N+1-ccw]>=dp[ccw][cw][ns].e0;
// assert(!cancollect);
dp[ccw+1][cw][ns+cancollect].e0 = min(dp[ccw+1][cw][ns+cancollect].e0, (X[N+1-ccw]-X[N+1-(ccw+1)])+dp[ccw][cw][ns].e0);
//dbg('j');
dp[ccw][cw+1][ns+cancollect].e1 = min(dp[ccw][cw+1][ns+cancollect].e1, X[cw+1]+(L-X[N+1-(ccw)]) + dp[ccw][cw][ns].e0);
}
}
}
}
ll outp=0;
for (ll ccw = 0; ccw <= N; ++ccw)
{
for (ll cw = 0; cw <= N; ++cw)
{
if (cw+ccw>N) continue;
for (ll ns = 0; ns <= N; ++ns)
{
dbgv(ns);
dbg( ccw << " " << cw << " ");
if (dp[ccw][cw][ns].e1<INFTY)
{
bool cancollect = T[cw]>=dp[ccw][cw][ns].e1;
outp = max(outp,ns+cancollect);
}
if (dp[ccw][cw][ns].e0 < INFTY)
{
bool cancollect = T[N+1-ccw]>=dp[ccw][cw][ns].e0;
outp = max(outp,ns+cancollect);
}
}
}
}
dbgv('h');
dbgfor (pll a : dp[1][0]) cerr << a.e0 << "," << a.e1 << "\n";
cout << outp;
}
