#include<bits/stdc++.h>
#define fi first
#define se second
#define eb emplace_back
#define mp make_pair
using namespace std;
typedef long double ld;
typedef long long ll;
typedef unsigned long long ull;
typedef __int128 i128;
template<typename T,typename U>
T ceil(T x, U y) {return (x>0?(x+y-1)/y:x/y);}
template<typename T,typename U>
T floor(T x, U y) {return (x>0?x/y:(x-y+1)/y);}
template<class T,class S>
bool chmax(T &a,const S b) {return (a<b?a=b,1:0);}
template<class T,class S>
bool chmin(T &a,const S b) {return (a>b?a=b,1:0);}
int popcnt(int x) {return __builtin_popcount(x);}
int popcnt(ll x) {return __builtin_popcountll(x);}
int topbit(int x) {return (x==0?-1:31-__builtin_clz(x));}
int topbit(ll x) {return (x==0?-1:63-__builtin_clzll(x));}
int lowbit(int x) {return (x==0?-1:__builtin_ctz(x));}
int lowbit(ll x) {return (x==0?-1:__builtin_ctzll(x));}

#define int long long
#define rep(i,a,b) for(int i=(a);i<=(b);i++)
#define per(i,a,b) for(int i=(a);i>=(b);i--)
typedef pair<int,int> pii;
typedef vector<int> vi;
typedef vector<pii> vp;
int read() {
  int x=0,w=1; char c=getchar(); 
  while(!isdigit(c)) {if(c=='-') w=-1; c=getchar();}
  while(isdigit(c)) {x=x*10+(c-'0'); c=getchar();}
  return x*w;
}

const int N=405,inf=0x3f3f3f3f3f3f3f3f;
int n,L,d[N],t[N],f[N][N][N>>1],g[N][N][N>>1],ans;

signed main() {
  n=read(), L=read();
  rep(i,1,n) d[i]=read();
  rep(i,1,n) t[i]=read();
  rep(i,1,n) d[i+n]=d[i]+L, t[i+n]=t[i];
  rep(l,1,2*n) rep(r,1,2*n) rep(x,0,n) f[l][r][x]=g[l][r][x]=inf;
  rep(i,1,n) {
    int x=(min(d[i],L-d[i])<=t[i]);
    f[i][i][0]=f[i+n][i+n][x]=min(d[i],L-d[i]);
    f[i][i][x]=f[i+n][i+n][x]=min(d[i],L-d[i]);
    g[i][i][0]=g[i+n][i+n][x]=min(d[i],L-d[i]);
    g[i][i][x]=g[i+n][i+n][x]=min(d[i],L-d[i]);
  }
  rep(len,2,n) {
    rep(l,1,2*n-len+1) {
      int r=l+len-1;
      rep(x,0,n) {
        int yl=((f[l+1][r][x]+d[l+1]-d[l])<=t[l]);
        chmin(f[l][r][x+yl],f[l+1][r][x]+d[l+1]-d[l]);
        int yr=((g[l][r-1][x]+d[r]-d[r-1])<=t[r]);
        chmin(g[l][r][x+yr],g[l][r-1][x]+d[r]-d[r-1]);
      }
      rep(x,0,n) {
        chmin(f[l][r][x],g[l][r][x]+d[r]-d[l]);
        chmin(g[l][r][x],f[l][r][x]+d[r]-d[l]);
        if(f[l][r][x]<inf) chmax(ans,x);
        if(g[l][r][x]<inf) chmax(ans,x);
      }
    }
  }
  printf("%lld\n",ans);
  return 0;
}