#include <bits/stdc++.h>
using namespace std;
#define foru(i,a,b) for(int i=(a); i<=(b); ++i)
#define ford(i,a,b) for(int i=(a); i>=(b); --i)
#define rep(i,a) for(int i=0; i<(a); ++i)
#define bit(s,i) (((s)>>(i))&1)
#define all(a) (a).begin(),(a).end()
#define sz(a) (int)(a).size()
#define ii pair<int,int>
#define fi first
#define se second
#define int long long
#define eb emplace_back
#define pb push_back
#define ll long long
#define __builtin_popcount(a) __builtin_popcountll(a)
template <class X, class Y>
bool maxi(X &x, Y y){
if(x<y){
x=y;
return true;
}
return false;
}
template <class X, class Y>
bool mini(X &x, Y y){
if(x>y){
x=y;
return true;
}
return false;
}
const int N=222;
int n,L,x[N],t[N]; ll dp[N][N][N][2],f[N],s[N];
void solve(){
cin>>n>>L;
foru(i,1,n) cin>>x[i];
foru(i,1,n) cin>>t[i];
x[n+1]=L;
foru(i,1,n) f[i]=f[i-1]+x[i]-x[i-1];
ford(i,n,1) s[i]=s[i+1]+x[i+1]-x[i];
memset(dp,0x3f,sizeof(dp));
int res=0;
dp[n+1][0][0][0]=dp[n+1][0][0][1]=0;
ford(i,n+1,1) foru(j,0,n) foru(k,0,n) if(i>j){
ll tim=dp[i][j][k][0],ntim=0;
ntim=tim+x[i]-x[i-1];
mini(dp[i-1][j][k+(ntim<=t[i-1])][0],ntim);
ntim=tim+s[i]+f[j+1];
mini(dp[i][j+1][k+(ntim<=t[j+1])][1],ntim);
tim=dp[i][j][k][1];
ntim=tim+x[j+1]-x[j];
mini(dp[i][j+1][k+(ntim<=t[j+1])][1],ntim);
ntim=tim+f[j]+s[i-1];
mini(dp[i-1][j][k+(ntim<=t[i-1])][0],ntim);
if(dp[i][j][k][0]<1e18) maxi(res,k);
if(dp[i][j][k][1]<1e18) maxi(res,k);
}
cout<<res<<'\n';
}
int32_t main(){
#define task "test"
if(fopen(task".inp","r")){
freopen(task".inp","r",stdin);
freopen(task".out","w",stdout);
}
cin.tie(0)->sync_with_stdio(0);
solve();
}
