#include <bits/stdc++.h>
#define fi first
#define se second
#define pb push_back
#define sz(a) (int)a.size()
#define all(a) a.begin(),a.end()
#define rep(i,n) for(int i=0;i<n;i++)
#define crep(i,x,n) for(int i=x;i<n;i++)
#define drep(i,n) for(int i=n-1;i>=0;i--)
#define vec(...) vector<__VA_ARGS__>
#define _34raRxL ios::sync_with_stdio(0),cin.tie(0)
using namespace std;
void print(){cout<<"\n";}
template<class te,class ...ti>
void print(const te&v,const ti&...nv){cout<<v;if(sizeof...(nv)){cout<<" ";print(nv...);}}
typedef long long ll;
typedef long double ld;
using pii=pair<int,int>;
using vi=vector<int>;
using vll=vector<long long>;
//e
const ll inf=1e18;
ll dp[203][203][203][2];
void chmin(ll &a,ll b){
a=min(a,b);
}
int main(){
_34raRxL;
int n,l;
cin>>n>>l;
vi a(n),ts(n);
{
rep(i,n){
cin>>a[i];
}
a.insert(a.begin(),0);
a.pb(l);
rep(i,n){
cin>>ts[i];
}
ts.insert(ts.begin(),0);
n+=2;
}
rep(i,n)rep(j,n)rep(k,n){
dp[i][j][k][0]=dp[i][j][k][1]=inf;
}
dp[0][n-1][0][0]=dp[0][n-1][0][1]=0;
rep(i,n){
drep(j,n){
rep(k,n-1){
ll vmi=inf,ad=0;
if(i+1<j){
vmi=min(dp[i][j][k][0]+a[i+1]-a[i],dp[i][j][k][1]+l-a[j]+a[i+1]);
ad=(ts[i+1]>=vmi);
chmin(dp[i+1][j][k+ad][0],vmi);
}
vmi=inf;
if(j-1>i){
vmi=min(dp[i][j][k][1]+a[j]-a[j-1],dp[i][j][k][0]+a[i]+l-a[j-1]);
ad=(ts[j-1]>=vmi);
chmin(dp[i][j-1][k+ad][1],vmi);
}
}
}
}
int ans=0;
rep(i,n){
rep(j,n){
rep(k,n-1){
if(dp[i][j][k][0]!=inf or dp[i][j][k][1]!=inf){
ans=max(ans,k);
}
}
}
}
print(ans,"\n");
//
return 0;
}
