#include <bits/stdc++.h>
using namespace std;
int dp[205][205][205][2], x[205], t[205], n, l;
int d(int i, int j)
{
return min(abs(x[i]-x[j]), l-abs(x[i]-x[j]));
}
int f(int l, int r, int c, int s)
{
if (!c)
return 1e9;
if (c>r-l+1)
return -1e9;
if (dp[l][r][c][s]!=-1e9)
return dp[l][r][c][s];
int ind, ans=-1e9;
if (s)
ind=r+1;
else
ind=l-1;
ans=max(ans, f(l+1, r, c, 0)-d(ind, l));
ans=max(ans, f(l, r-1, c, 1)-d(ind, r));
ans=max(ans, min(f(l+1, r, c-1, 0), t[l])-d(ind, l));
ans=max(ans, min(f(l, r-1, c-1, 1), t[r])-d(ind, r));
dp[l][r][c][s]=ans;
return ans;
}
int main()
{
ios::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];
for (int i=1; i<=n; i++)
for (int j=i; j<=n; j++)
for (int k=1; k<=j-i+1; k++)
dp[i][j][k][0]=dp[i][j][k][1]=-1e9;
for (int i=1; i<=n; i++)
{
if (f(1, n, i, 0)<0)
{
cout << i-1;
return 0;
}
}
cout << n;
return 0;
}
