#include <bits/stdc++.h>
#pragma GCC optimize("O3")
#define int long long
#define ll long long
#define pb push_back
#define fi first
#define se second
#define lf (id<<1)
#define rg ((id<<1)|1)
#define md ((l+r)>>1)
#define ld long double
using namespace std;
typedef pair<int,int> pii;
typedef pair<char,char> pcc;
typedef pair<int,pii> ipii;
typedef pair<pii,pii> ipiii;
const int MAXN = 1e5+10;
const int MAXA = 1e6;
const int INF = 1e18+10;
const int MOD = 1e9+7;
const int LOG = 21;
const ld EPS = 1e-12;
void chmx(int &a, int b){ a = max(a, b); }
int n, l;
int x[210], t[210];
int dp[210][210][210][3];
signed main(){
// ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
cin >> n >> l;
for(int i=1; i<=n; i++) cin >> x[i];
for(int i=1; i<=n; i++) cin >> t[i];
x[n+1] = l;
for(int i=0; i<=n+1; i++)
for(int j=0; j<=n+1; j++)
for(int k=0; k<=200; k++)
dp[i][j][k][0] = -INF, dp[i][j][k][1] = -INF;
dp[0][n+1][0][0] = dp[0][n+1][0][1] = 0;
int ans = 0;
for(int k=1; k<=200; k++){
for(int i=0; i<=n; i++){
for(int j=i+1; j<=n+1; j++){
if(i!=0){
int val = (k<=t[i]);
int oth = k - (x[i]-x[i-1]);
if(oth>=0)
chmx(dp[i][j][k][0], dp[i-1][j][oth][0]+val);
oth = k - (x[i] + l-x[j]);
if(oth>=0)
chmx(dp[i][j][k][0], dp[i-1][j][oth][1]+val);
}
if(j!=n+1){
int val = (k<=t[j]);
int oth = k - (x[j+1]-x[j]);
if(oth>=0)
chmx(dp[i][j][k][1], dp[i][j+1][oth][1]+val);
oth = k - (l-x[j] + x[i]);
if(oth>=0)
chmx(dp[i][j][k][1], dp[i][j+1][oth][0]+val);
}
chmx(ans, max(dp[i][j][k][0], dp[i][j][k][1]) );
}
}
}
// cout << dp[0][4][7][1] << " pp\n";
cout << ans << '\n';
}
