//challenge: 100
#include<bits/stdc++.h>
using namespace std;
#define int long long
#define v vector
int n,L;
vector<int> x,t;
v<v<v<v<int>>>> dp;
const int INF=1e18;
int dis(int a,int b){
return min(abs(x[a]-x[b]),L-abs(x[a]-x[b]));
}
int f(int l,int r,int cnt,int s){
if(cnt==0){
return INF;
}
if(r-l+1<cnt){
return -INF;
}
if(dp[l][r][cnt][s]!=-INF){
return dp[l][r][cnt][s];
}
int now=0;
if(s==0){
now=l-1;
}
else{
now=r+1;
}
dp[l][r][cnt][s]=max(dp[l][r][cnt][s],f(l+1,r,cnt,0)-dis(now,l));
dp[l][r][cnt][s]=max(dp[l][r][cnt][s],f(l,r-1,cnt,1)-dis(now,r));
dp[l][r][cnt][s]=max(dp[l][r][cnt][s],min(f(l+1,r,cnt-1,0),t[l])-dis(now,l));
dp[l][r][cnt][s]=max(dp[l][r][cnt][s],min(f(l,r-1,cnt-1,1),t[r])-dis(now,r));
return dp[l][r][cnt][s];
}
signed main(){
ios_base::sync_with_stdio(false);
cin.tie(0);
cin>>n>>L;
t.resize(n+2);
x.resize(n+2);
for(int i=1;i<=n;i++){
cin>>x[i];
}
for(int i=1;i<=n;i++){
cin>>t[i];
}
dp.resize(n+2,v<v<v<int>>>(n+2,v<v<int>>(n+2,v<int>(2,-INF))));
int ans=0;
for(int i=1;i<=n;i++){
if(f(1,n,i,0)>=0){
ans=i;
}
}
cout<<ans<<endl;
return 0;
}
