#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const ll INF = 1e18+7;
const ll MOD = 998244353;
typedef pair<ll,ll> ii;
#define iii pair<ll,ii>
#define f(i,a,b) for(ll i = a;i < b;i++)
#define pb push_back
#define vll vector<ll>
#define F first
#define S second
#define all(x) (x).begin(), (x).end()
///I hope I will get uprating and don't make mistakes
///I will never stop programming
///sqrt(-1) Love C++
///Please don't hack me
///@TheofanisOrfanou Theo830
///Think different approaches (bs,dp,greedy,graphs,shortest paths,mst)
///Stay Calm
///Look for special cases
///Beware of overflow and array bounds
///Think the problem backwards
///Training
int main(){
ios_base::sync_with_stdio(0);
cin.tie(0);
ll n;
cin>>n;
ll l;
cin>>l;
ll x[n+2];
x[0] = 0;
f(i,1,n+1){
cin>>x[i];
}
x[n+1] = l;
ll t[n+2];
t[0] = t[n+1] = -1;
f(i,1,n+1){
cin>>t[i];
}
ll dp[205][205][205][2];
f(i,0,n+5){
f(j,0,n+5){
f(k,0,n+5){
f(u,0,2){
dp[i][j][k][u] = INF;
}
}
}
}
ll ans = 0;
f(i,0,n+1){
f(j,0,n+1){
if(i + j <= n){
f(k,0,n+1){
if(k == 0){
dp[i][j][k][0] = dp[i][j][k][1] = l - x[n+1-i] + x[j];
}
dp[i][j+1][k][0] = min({dp[i][j+1][k][0],dp[i][j][k][0] + x[j+1] - x[j],dp[i][j][k][1] + l - x[n+1-i] + x[j+1]});
dp[i+1][j][k][1] = min({dp[i+1][j][k][1],dp[i][j][k][1] + x[n+1-i] - x[n-i],dp[i][j][k][0] + x[j] + l - x[n+1-i]});
if(min(dp[i][j][k][0] + x[j+1] - x[j],dp[i][j][k][1] + l - x[n+1-i] + x[j+1]) <= t[j+1]){
dp[i][j+1][k+1][0] = min({dp[i][j+1][k+1][0],dp[i][j][k][0] + x[j+1] - x[j],dp[i][j][k][1] + l - x[n+1-i] + x[j+1]});
}
if(min(dp[i][j][k][1] + x[n+1-i] - x[n-i],dp[i][j][k][0] + x[j] + l - x[n+1-i]) <= t[n-i]){
dp[i+1][j][k+1][1] = min({dp[i+1][j][k+1][1],dp[i][j][k][1] + x[n+1-i] - x[n-i],dp[i][j][k][0] + x[j] + l - x[n+1-i]});
}
//cout<<i<<" "<<j<<" "<<k<<" "<<dp[i][j][k][0]<<" "<<dp[i][j][k][1]<<"\n";
f(u,0,2){
if(dp[i][j][k][u] < INF){
ans = max(ans,k);
}
}
}
}
}
}
cout<<ans<<"\n";
}
