#include<bits/stdc++.h>
#define ll long long
#define ff first
#define ss second
#define pb push_back
using namespace std;
const int N = 1e6 + 69;
int n,k,l,r,ans;
ll dro,x,L;
ll A[N],T[N];
ll dp[202][202][202][2];
ll dist(ll x,ll y){
return min(abs(x-y),L-abs(x-y));
}
int main(){
cin>>n>>L;
for(int i=1;i<=n;i++){
cin>>A[i];
}
A[n+1] = L;
for(int i=1;i<=n;i++){
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 t=0;t<=1;t++)
dp[i][j][k][t] = 1e18;
}
}
}
dp[0][0][0][1] = dp[0][0][0][0] = 0;
for(int i=0;i<=n;i++){
for(int j=0;j<=n-i;j++){
for(int k=0;k<=i+j;k++){
x = dp[i][j][k][0];
if(x<1e18){
ans = max(k,ans);
}
dro = x + dist(A[i+1], A[i]);
dp[i+1][j][k+(dro<=T[i+1])][0] = min(dp[i+1][j][k+(dro<=T[i+1])][0],dro);
dro = x + dist(A[i], A[n-j]);
dp[i][j+1][k+(dro<=T[n-j])][1] = min(dp[i][j+1][k+(dro<=T[n-j])][1],dro);
x = dp[i][j][k][1];
if(x<1e18){
ans = max(k,ans);
}
dro = x + dist( A[i+1], A[n+1-j]);
dp[i+1][j][k+(dro<=T[i+1])][0] = min(dp[i+1][j][k+(dro<=T[i+1])][0],dro);
dro = x + dist(A[n+1-j],A[n-j]);
dp[i][j+1][k+(dro<=T[n-j])][1] = min(dp[i][j+1][k+(dro<=T[n-j])][1],dro);
}
}
}
cout<<ans<<endl;
}
