#include<bits/stdc++.h>
#define int long long
using namespace std;
int32_t main()
{
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
int n,l;
cin >> n>>l;
vector<vector<vector<int>>> a(n+2,vector<vector<int>>(n+2,vector<int>(n+1,1e18))),b(n+2,vector<vector<int>>(n+2,vector<int>(n+1,1e18)));
a[0][n+1][0] = b[0][n+1][0] = 0;
vector<int> x(n+2,0),tim(n+2,-1);
x[n+1] = l;
for(int i=1;i<=n;i++) cin >> x[i];
for(int i=1;i<=n;i++) cin >> tim[i];
int ans = 0;
for(int say = 0;say<=n;say++)
{
for(int i =0;i<=n+1;i++)
{
for(int j = n+1;j>=0;j--)
{
if(i>=j) continue;
if(i>0)
{
a[i][j][say] = min(a[i][j][say],a[i-1][j][say]+x[i]-x[i-1]);
a[i][j][say] = min(a[i][j][say],b[i-1][j][say]+x[i]+l-x[j]);
}
if(j<=n)
{
b[i][j][say] = min(b[i][j][say],b[i][j+1][say]+x[j+1]-x[j]);
b[i][j][say] = min(b[i][j][say],a[i][j+1][say]+l-x[j]+x[i]);
}
if(say==0) continue;
int cur;
if(i>0)
{
cur = a[i-1][j][say-1]+x[i]-x[i-1];
if(cur<=tim[i])
{
a[i][j][say] = min(a[i][j][say],cur);
}
cur = b[i-1][j][say-1]+x[i]+l-x[j];
if(cur<=tim[i])
{
a[i][j][say] = min(a[i][j][say],cur);
}
}
if(j<=n)
{
cur = b[i][j+1][say-1]+x[j+1]-x[j];
if(cur<=tim[j])
{
b[i][j][say] = min(b[i][j][say],cur);
}
cur = a[i][j+1][say-1]+x[i]+l-x[j];
if(cur<=tim[j])
{
b[i][j][say] = min(b[i][j][say],cur );
}
}
if(a[i][j][say]<1e18 || b[i][j][say]<1e18)
{
ans = max(ans,say);
// cout << ans << " "<<i << " "<< j<< " "<<a[i][j][say] << " "<< b[i][j][say] << endl;
}
//cout << i << " "<< j << " "<< say << " " << a[i][j][say] << " "<< b[i][j][say] << endl;
}
}
}
cout << ans << endl;
}
