#include <bits/stdc++.h>
using namespace std;
#define int long long
#define faster ios_base::sync_with_stdio(false);cin.tie(NULL);cout.tie(NULL);
#define FOR for(int i=1;i<=n;i++)
#define lim 205
#define DP dp[i][j][k][l]
int n,l;
int x[lim],t[lim];
int dp[lim][lim][lim][2];
//0 sol
//1 sag
int32_t main(){
faster
cin>>n>>l;
FOR{
cin>>x[i];
}
x[n+1]=l;
FOR{
cin>>t[i];
}
for(int i=0;i<=n;i++){
for(int j=0;j<=n;j++){
for(int k=0;k<=n;k++){
for(int l=0;l<=1;l++)DP=LLONG_MAX;
}
}
}
dp[0][0][0][0]=dp[0][0][0][1]=0;
for(int i=0;i<=n;i++){
for(int j=0;j<=n-i;j++){
for(int k=0;k<=i+j;k++){
//soldan
int zaman=x[i+1]-x[i]+dp[i][j][k][0];
if(dp[i][j][k][0]==LLONG_MAX)zaman=LLONG_MAX;
int ol=0;
if(zaman<=t[i+1])ol=1;
dp[i+1][j][k+ol][0]=min(dp[i+1][j][k+ol][0],zaman);
zaman=x[i]+l-x[n-j]+dp[i][j][k][0];
if(dp[i][j][k][0]==LLONG_MAX)zaman=LLONG_MAX;
ol=0;
if(zaman<=t[n-j])ol=1;
dp[i][j+1][k+ol][1]=min(dp[i][j+1][k+ol][1],zaman);
// sagdan
zaman=x[n-(j-1)]-x[n-j]+dp[i][j][k][1];
if(dp[i][j][k][1]==LLONG_MAX)zaman=LLONG_MAX;
ol=0;
if(zaman<=t[n-j])ol=1;
dp[i][j+1][k+ol][1]=min(dp[i][j+1][k+ol][1],zaman);
zaman=l-x[n-(j-1)]+x[i+1]+dp[i][j][k][1];
if(dp[i][j][k][1]==LLONG_MAX)zaman=LLONG_MAX;
ol=0;
if(zaman<=t[i+1])ol=1;
dp[i+1][j][k+ol][0]=min(dp[i+1][j][k+ol][0],zaman);
}
}
}
int cev=0;
for(int i=0;i<=n;i++){
for(int j=0;j<=n;j++){
for(int k=0;k<=n;k++){
for(int l=0;l<=1;l++){
//cout<<DP<<" "<<i<<" "<<j<<" "<<k<<" "<<l<<endl;
if(i+j==n && DP!=LLONG_MAX)cev=max(cev,k);
}
}
}
}
cout<<cev<<'\n';
return 0;
}
