#define here cerr<<"===========================================\n"
#define dbg(x) cerr<<#x<<": "<<x<<endl;
#include <bits/stdc++.h>
#include <ext/pb_ds/tree_policy.hpp>
#include <ext/pb_ds/assoc_container.hpp>
#define ld double
#define ll long long
#define llinf 100000000000000000LL // 10^17
#define pb push_back
#define popb pop_back
#define fi first
#define sc second
#define endl '\n'
#define pll pair<ll,ll>
#define pld pair<ld,ld>
#define sz(a) (ll)(a.size())
#define all(a) a.begin(),a.end()
#define ceri(a,l,r) {cerr<<#a<<": ";for(ll i_ = l;i_<=r;i_++) cerr<<a[i_]<< " ";cerr<<endl;}
#define daj_mi_malo_vremena ios_base::sync_with_stdio(false);cerr.tie(0);cout.tie(0);cin.tie(0);
using namespace std;
using namespace __gnu_pbds;
/*
ll add(ll x,ll y){
x+=y;
if(x<0){
x%=mod;
x+=mod;
}else{
if(x>=mod) x%=mod;
}
return x;
}
ll mul(ll a,ll b){
ll ans = (a*b)%mod;
if(ans<0) ans+=mod;
return ans;
}
typedef tree<int,null_type,less<ll>,rb_tree_tag,tree_order_statistics_node_update> ordered_set;
typedef tree<int,null_type,less_equal<ll>,rb_tree_tag,tree_order_statistics_node_update> ordered_multiset;
mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());
ll rnd(ll l,ll r){
return uniform_int_distribution<ll>(l,r)(rng);
}
*/
void ckmin(ll &x,ll y){x = min(x,y);}
#define maxn 205
ll n,L;
ll a[maxn],t[maxn];
ll b[maxn];
ll dp[maxn][maxn][2][maxn];
int main(){
daj_mi_malo_vremena
cin >> n >> L;
for(ll i = 1;i<=n;i++) cin >> a[i];
for(ll i = 1;i<=n;i++) b[i] = L-a[i];
reverse(b+1,b+n+1);
for(ll i = 1;i<=n;i++) cin >> t[i];
for(ll i = 0;i<=n;i++) for(ll j = 0;j<=n;j++) for(ll e = 0;e<=1;e++) for(ll p = 0;p<=n;p++)
dp[i][j][e][p] = llinf;
dp[1][0][1][a[1]<=t[1]] = a[1];
dp[1][0][1][0] = a[1];
dp[0][1][0][b[1]<=t[n]] = b[1];
dp[0][1][0][0] = b[1];
for(ll s = 1;s<n;s++){
for(ll l = 0;l<=s;l++){
ll r = s-l;
for(ll e = 0;e<=1;e++){
for(ll p = 0;p<=n;p++){
ll time = dp[l][r][e][p];
ll dl = a[l+1]-a[l];
if(!e) dl = b[r] + a[l+1];
ll dr = b[r+1] + a[l];
if(!e) dr = b[r+1] - b[r];
if(s==n-1) dl = min(a[l+1]-a[l],b[r]+a[l+1]);
if(s==n-1) dr = min(b[r+1]-b[r],b[r+1]+a[l]);
ckmin(dp[l+1][r][1][p+((time+dl)<=t[l+1])],time+dl);
ckmin(dp[l][r+1][0][p+((time+dr)<=t[n-(r+1)+1])],time+dr);
}
}
}
}
ll ans = 0;
for(ll s = 1;s<=n;s++){
for(ll l = 0;l<=s;l++){
ll r = s-l;
for(ll e = 0;e<=1;e++){
for(ll p = 0;p<=n;p++){
if(dp[l][r][e][p]<llinf) ans = max(ans,p);
}
}
}
}
cout<<ans<<endl;
return 0;
}
