#include<bits/stdc++.h>
using namespace std;
bool M1;
#define PI 3.14159265358979323846
#define sz(a) (int)a.size()
#define all(x) x.begin(),x.end()
#define ii pair<int,int>
#define iii pair<int,ii>
#define iv pair<ii,ii>
#define se second
#define fi first
#define ffi fi.fi
#define sfi se.fi
#define sse se.se
#define fse fi.se
#define lt(i, c, d) for(int i = c; i <= d; ++i)
#define fl(i, c, d) for(int i = d; i >= c; --i)
#define pb push_back
#define emb emplace_back
#define emf emplace_front
#define em emplace
#define look_memory cerr<<abs(&M2-&M1)/1024.0/1024<<'\n'
#define look_time cerr << "TIME : " << clock() * 0.001 << "s" <<'\n'
const int N=2e2+5,lg=30,mod=1e9+7;
mt19937 rd(chrono::steady_clock::now().time_since_epoch().count());
int Rand(int u,int v){
return u+rd()%(v-u+1);
}
int dx[]={1,0,-1,0,1,1,-1,-1};
int dy[]={0,-1,0,1,1,-1,1,-1};
int node,l,x[N],t[N];
int dp[N][N][N][2];
int kc(int u,int v){
return min(l-abs(x[u]-x[v]),abs(x[u]-x[v]));
}
bool M2;
void solve(){
cin >> node >> l;
for(int i=1;i<=node;++i)cin >> x[i];
for(int i=1;i<=node;++i)cin >> t[i];
memset(dp,0x3f,sizeof dp);
dp[0][node+1][0][0]=0;
int ans=0;
queue<tuple<int,int,int,int>>p;
p.em(0,node+1,0,0);
while(!p.empty()){
auto [l,r,i,huong]=p.front();
// cout <<w<<" "<<l<<" "<<r<<" "<<i<<" "<<huong<<'\n';
p.pop();
ans=max(ans,i);
if(l+1<r)
{
int val=dp[l][r][i][huong]+(huong==0?kc(l,l+1):kc(r,l+1));
int newi=i+(val<=t[l+1]);
if(dp[l+1][r][newi][0]>val){
dp[l+1][r][newi][0]=val;
p.em(l+1,r,newi,0);
}
}
if(l<r-1)
{
int val=dp[l][r][i][huong]+(huong==0?kc(l,r-1):kc(r,r-1));
int newi=i+(val<=t[r-1]);
if(dp[l][r-1][newi][1]>val){
dp[l][r-1][newi][1]=val;
p.em(l,r-1,newi,1);
}
}
}
cout << ans;
}
main()
{
srand(time(0));
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cout.tie(NULL);
#define task "aws"
if(fopen(task".inp","r")){
freopen(task".inp","r",stdin);
freopen(task".out","w",stdout);
}
int t=1;
// cin >> t;
while(t--){
solve();cout<<'\n';
}
look_memory;
look_time;
}
