#include <bits/stdc++.h>
using namespace std;
#define int long long
#define FOR(i,a,b) for(int i=a;i<=(int)b;i++)
#define FORD(i,a,b) for(int i=a;i>=(int)b;i--)
#define ll long long
#define fi first
#define se second
#define pb push_back
#define all(a) a.begin(),a.end()
#define BIT(mask,i) ((mask>>(i))&1)
#define MASK(a) (1LL<=((a)))
#define uni(v) sort(all(v)); v.resize(unique(all(v)) - v.begin())
#define pii pair <int, int>
#define vi vector <int>
#define vl vector <ll>
template <class A,class B>
bool maximize(A &a, const B b)
{
if(a < b){ a = b; return 1;} return 0;
}
template <class A,class B>
bool minimize(A &a, const B b)
{
if(a > b){ a = b; return 1;} return 0;
}
const int maxn = 200 + 5;
int n, L;
int X[maxn], T[maxn];
int dp[maxn][maxn][maxn][3];
int dist(int x, int y)
{
return min(L - abs(x - y), abs(x - y));
}
void solve()
{
cin >> n >> L;
FOR(i, 1, n) cin >> X[i];
FOR(i, 1, n) cin >> T[i];
memset(dp, 0x3f, sizeof dp);
X[n + 1] = 0;
dp[n + 1][0][0][0] = 0;
queue <array <int, 4>> que;
que.push({n + 1, 0, 0, 0});
int ans = 0;
while(!que.empty())
{
int l = que.front()[0], r = que.front()[1], cnt = que.front()[2], t = que.front()[3];
int curT = dp[l][r][cnt][t];
que.pop();
maximize(ans, cnt);
// mo rong l
{
int newl = l - 1;
if(newl <= r) continue;
int newT = (t == 1 ? dist(X[r], X[newl]) : dist(X[l], X[newl])) + curT;
int newcnt = (newT <= T[newl]) + cnt;
if(minimize(dp[newl][r][newcnt][0], newT))
{
que.push({newl, r, newcnt, 0});
}
}
{
int newr = r + 1;
if(newr >= l) continue;
int newT = (t == 1 ? dist(X[r], X[newr]) : dist(X[l], X[newr])) + curT;
int newcnt = (newT <= T[newr]) + cnt;
if(minimize(dp[l][newr][newcnt][1], newT))
{
que.push({l, newr, newcnt, 1});
}
}
}
cout << ans;
}
signed main()
{
ios_base::sync_with_stdio(0);
cin.tie(0); cout.tie(0);
#define kieuoanh "joi20_ho_t3"
if(fopen(kieuoanh".inp","r"))
{
freopen(kieuoanh".inp","r",stdin);
freopen(kieuoanh".out","w",stdout);
}
int tst = 1;
// cin >> tst;
while(tst--) solve();
return 0;
}
