#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define pb push_back
#define ff first
#define ss second
#define all(s) s.begin(),s.end()
#define rall(s) s.rbegin(),s.rend()
//try
template<class T> T &chmax(T &a,const T &b){ return a = max(a,b); }
template<class T> T &chmin(T &a,const T &b){ return a = min(a,b); }
int main(){
ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0);
ll n,L;
cin>>n>>L;
ll x[n+5],t[n+5];
for(ll i=1;i<=n;i++){
cin>>x[i];
}
for(ll i=1;i<=n;i++){
cin>>t[i];
}
x[0]=0;
function <ll(ll,ll)> dist=[&](ll a,ll b){
return min(abs(x[a]-x[b]),L-abs(x[a]-x[b]));
};
ll dp[1<<n][n+5][n+5];
for(ll i=0;i<(1<<n);i++){
for(ll j=0;j<=n;j++){
for(ll k=0;k<=n;k++){
dp[i][j][k]=1e18;
}
}
}
dp[0][0][0]=0;
for(ll s=0;s<(1<<n);s++){
for(ll i=0;i<=n;i++){
if(i==0||(s&(1<<(i-1)))){
for(ll k=0;k<=n;k++){
if(dp[s][i][k]==1e18) continue;
for(ll j=0;j<n;j++){//next pos 0-indexed
if((s&(1<<j))==0){//currently not stamped j
chmin(dp[s|(1<<j)][j+1][k+(dp[s][i][k]+dist(i,j+1)<=t[j+1])],dp[s][i][k]+dist(i,j+1));
}
}
}
}
}
}
ll ans=0;
for(ll s=0;s<(1<<n);s++){
for(ll i=0;i<=n;i++){
for(ll k=0;k<=n;k++){
if(dp[s][i][k]!=1e18){
ans=max(ans,k);
}
}
}
}
cout<<ans;
}
