#include <bits/stdc++.h>
using namespace std;
#define cin(vec) for(auto& i : vec) cin >> i
#define cout(vec) for(auto& i : vec) cout << i << " "; cout << "\n";
#define fast ios::sync_with_stdio(0);cin.tie(0);
#define loop(i,a,b) for (int i = a; i < b; i++)
#define F first
#define S second
#define pb(n) push_back(n)
#define pf(n) push_front(n)
#define dci(d) fixed<<setprecision(d)
#define sp ' '
#define el '\n'
#define all(v) v.begin(),v.end()
#define int long long
int dx[8]= {0,0,1,-1,-1,1,1,-1};
int dy[8]= {-1,1,0,0,-1,1,-1,1};
int const N=1e4+5,M=1e3+1,Mod=1e9+7;
int a[202],t[202],n,len;
map<pair<pair<pair<int,int>,int>,int>,int>m;
map<pair<pair<pair<int,int>,int>,int>,bool>vis;
int rec(int l,int r,int loc,int time){
if(l==r){
return 0;
}
if(vis[make_pair(make_pair(make_pair(l,r),loc),time)]){
return m[make_pair(make_pair(make_pair(l,r),loc),time)];
}
vis[make_pair(make_pair(make_pair(l,r),loc),time)]=1;
int mx=0;
if(!loc){
mx=max(rec(l-1,r,0,time+(a[l]-a[l-1]))+((time+(a[l]-a[l-1]))<=t[l-1])
,rec(l-1,r,1,time+(len-a[l])+a[r])+((time+(len-a[l])+a[r])<=t[r]));
}
else{
mx=max(rec(l,r+1,0,time+(len-a[l])+a[r])+((time+(len-a[l])+a[r])<=t[l])
,rec(l,r+1,1,time+(a[r+1]-a[r]))+((time+(a[r+1]-a[r]))<=t[r+1]));
}
// if(l==5&&r==1)
// cout<<l<<' '<<r<<' '<<loc<<' '<<time<<' '<<mx<<el;
return m[make_pair(make_pair(make_pair(l,r),loc),time)]=mx;
}
void testcase(int h){
cin>>n>>len;
for(int i=1;i<=n;i++)cin>>a[i];
for(int i=1;i<=n;i++)cin>>t[i];
cout<<max(rec(n,1,0,len-a[n])+(len-a[n]<=t[n]),rec(n,1,1,a[1])+(a[1]<=t[1]));
}
int32_t main()
{
// fast
testcase(1);
// int tc;cin>>tc;for(int i=1;i<=tc;i++)testcase(i);
return 0;
}
