#include <bits/stdc++.h>
#define fst first
#define snd second
#define pb push_back
#define forn(i,a,b) for(int i= a; i<b; i++)
#define ALL(x) x.begin(),x.end()
#define SZ(x) (int)x.size()
#define mset(a,v) memset(a,v,sizeof(a))
#define FIN ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
using namespace std;
typedef long long ll;
#ifdef D
#define debug(x) cout << x
#else
#define debug(x) //nothing
#endif
#define INF ((ll)1000000000)
const int MAXN = 201;
struct Node{
ll left;
ll right;
ll type; // 0 left 1 right
ll cnt;
Node(ll left, ll right,ll type, ll cnt): left(left), right(right), type(type) , cnt(cnt) {}
};
bool operator<(const Node &a, const Node &b){
if(a.cnt!=b.cnt) return a.cnt<b.cnt;
if(a.right-a.left !=b.right-b.left) return a.right-a.left < b.right-b.left;
return a.type<b.type;
}
vector<pair<ll,ll>> point;
ll n,L;
//IMPORTANTE
//acordarse de tener punto 1
ll best = 0;
ll dist[MAXN][MAXN][3][MAXN];
void dijkstra(){
mset(dist,-1);
priority_queue<pair<ll,Node>> pq; pq.push({0,Node(0,SZ(point)-1,0,0)});
while(!pq.empty()){
ll cost = pq.top().fst*-1;
Node rnd = pq.top().snd;
ll l = rnd.left;
ll r = rnd.right;
ll t = rnd.type;
ll cnt = rnd.cnt;
pq.pop();
if(dist[l][r][t][cnt]!=-1) continue;
/*cout<<l<<" "<<r<<" "<<t<<" "<<cnt<<" "<<cost<<'\n';
cout<<point[l].fst<<" -- "<<point[r].fst<<'\n';*/
dist[l][r][t][cnt]=cost;
best=max(best, cnt);
if(t==1){
{
ll nl = l;
ll nr = r-1;
ll nt = t;
if(nl<nr){
ll ncost = cost + abs(point[r].fst-point[nr].fst);
ll ncnt = cnt + (ncost<=point[nr].snd?1:0);
if(dist[nl][nr][nt][ncnt]==-1) pq.push({ncost*-1, Node( nl, nr, nt, ncnt )});
}
}
{
ll nl = l+1;
ll nr = r;
ll nt = (t+1)%2;
if(nl<nr){
ll ncost = cost + abs((L-point[r].fst)+point[nl].fst);
ll ncnt = cnt + (ncost<=point[nl].snd?1:0);
if(dist[nl][nr][nt][ncnt]==-1) pq.push({ncost*-1, Node( nl, nr, nt, ncnt )});
}
}
}else{
{
ll nl = l;
ll nr = r-1;
ll nt = (t+1)%2;
if(nl<nr){
ll ncost = cost + abs((L-point[nr].fst)+point[l].fst);
ll ncnt = cnt + (ncost<=point[nr].snd?1:0);
if(dist[nl][nr][nt][ncnt]==-1) pq.push({ncost*-1, Node( nl, nr, nt, ncnt )});
}
}
{
ll nl = l+1;
ll nr = r;
ll nt = t;
if(nl<nr){
ll ncost = cost + abs(point[l].fst-point[nl].fst);
ll ncnt = cnt + (ncost<=point[nl].snd?1:0);
if(dist[nl][nr][nt][ncnt]==-1) pq.push({ncost*-1, Node( nl, nr, nt, ncnt )});
}
}
}
}
}
int main(){ FIN;
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;
dijkstra();
cout<<best<<'\n';
return 0;
}
