#include <bits/stdc++.h>
#define fst first
#define snd second
#define pb push_back
#define SZ(x) (int)x.size()
#define ALL(x) x.begin(),x.end()
#define forn(i,a,b) for(int i = a; i<b; i++)
#define mset(a,v) memset(a,v,sizeof(a))
#define FIN ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
#ifdef D
#define debug(x) cout << x
#else
#define debug(x) //nothing
#endif
using namespace std;
typedef long long ll;
const int MAXN = 205;
#define INF ((ll)10000000000000000)
ll dp[MAXN][MAXN][3][MAXN];
ll N,L;
vector<pair<ll,ll>> point;
ll f(ll l , ll r, ll t, ll cnt){
ll &res = dp[l][r][t][cnt];
if(res!=-1) return res;
if(l==0 && r==SZ(point)-1 && cnt==0) return res=0;
if(l==0 && r==SZ(point)-1) return res=INF;
res = INF;
if(t==0){
{
if(l-1>=0){
// estoy en el extramo izq viniendo desde el extremo izq
ll ncost = abs(point[l-1].fst-point[l].fst);
res=min(res, f(l-1, r, t, cnt)+ncost);
if(cnt>0 && f(l-1,r,t,cnt-1)+ncost<=point[l].snd){
res=min(res , f(l-1,r,t,cnt-1)+ncost );
}
//extremo izq viniendo desde el extremo der
ncost = L-point[r].fst + point[l].fst;
res=min(res , f(l-1,r,(t+1)%2,cnt)+ncost);
if(cnt>0 && f(l-1,r,(t+1)%2,cnt-1)+ncost<=point[l].snd){
res=min(res, f(l-1,r,(t+1)%2,cnt-1)+ncost);
}
}
}
}else{
{
if(r+1<SZ(point)){
// estoy en el extramo der viniendo desde el extremo der
ll ncost = point[r+1].fst-point[r].fst;
res=min(res, f(l, r+1, t, cnt)+ncost);
if(cnt>0 && f(l,r+1,t,cnt-1)+ncost<=point[r].snd){
res=min(res , f(l,r+1,t,cnt-1)+ncost );
}
//extremo der viniendo desde el extremo izq
ncost = L-point[r].fst + point[l].fst;
res=min(res , f(l,r+1,(t+1)%2,cnt)+ncost);
if(cnt>0 && f(l,r+1,(t+1)%2,cnt-1)+ncost<=point[r].snd){
res=min(res, f(l,r+1,(t+1)%2,cnt-1)+ncost);
}
}
}
}
return res;
}
int main(){
cin>>N>>L;
point.clear();
point.resize(N+2);
point[0]={0,-1};
point[N+1]={L,-1};
forn(i,1,N+1) cin>>point[i].fst;
forn(i,1,N+1) cin>>point[i].snd;
mset(dp,-1);
ll best = 0;
forn(l,0,N+1){
forn(r,l+1,N+2){
forn(t,0,3){
forn(cnt,0,N+1){
if(f(l,r,t,cnt)<INF){
best=max(best,(ll)cnt);
}
}
}
}
}
cout<<best<<'\n';
return 0;
}
