#include <ext/pb_ds/assoc_container.hpp>
#include <bits/stdc++.h>
using namespace __gnu_pbds;
using namespace std;
//#define int long long
const int SIZE = 210;
const int INF = 1e9 + 9;
const long long INFL = 1e18 + 9;
int dp[SIZE][SIZE][SIZE][2];
signed main()
{
for (int i = 0; i < SIZE; ++i)
{
for (int j = 0; j < SIZE; ++j)
{
for (int k = 0; k < SIZE; ++k)
{
dp[i][j][k][0] = INF;
dp[i][j][k][1] = INF;
}
}
}
ios::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
// freopen("input.txt", "r", stdin);
// freopen("output.txt", "w", stdout);
int n, l;
cin >> n >> l;
vector <int> x(n + 1);
x[0] = 0;
for (int i = 1; i <= n; ++i)
{
cin >> x[i];
}
vector <int> t(n + 1);
t[0] = -1;
for (int i = 1; i <= n; ++i)
{
cin >> t[i];
}
int gans = 0;
dp[0][0][0][0] = 0;
for (int ans = 0; ans <= n; ++ans)
{
for (int ll = 0; ll <= n; ++ll)
{
for (int rr = 0; rr <= n; ++rr)
{
if (dp[ans][ll][rr][0] != INF || dp[ans][ll][rr][1] != INF)
gans = max(ans, gans);
if (ll + rr >= n)
{
continue;
}
if (dp[ans][ll][rr][0] != INF)
{
int tt = dp[ans][ll][rr][0] + x[ll + 1] - x[ll];
if (tt <= t[ll + 1])
{
dp[ans + 1][ll + 1][rr][0] = min(dp[ans + 1][ll + 1][rr][0], tt);
}
else
{
dp[ans][ll + 1][rr][0] = min(dp[ans][ll + 1][rr][0], tt);
}
tt = dp[ans][ll][rr][0] + l - (x[n - rr] - x[ll]);
if (tt <= t[n - rr])
{
dp[ans + 1][ll][rr + 1][1] = min(dp[ans + 1][ll][rr + 1][1], tt);
}
else
{
dp[ans][ll][rr + 1][1] = min(dp[ans][ll][rr + 1][1], tt);
}
}
if (dp[ans][ll][rr][1] != INF)
{
int tt = dp[ans][ll][rr][1] + x[n - rr + 1] - x[n - rr];
if (tt <= t[n - rr])
{
dp[ans + 1][ll][rr + 1][1] = min(dp[ans + 1][ll][rr + 1][1], tt);
}
else
{
dp[ans][ll][rr + 1][1] = min(dp[ans][ll][rr + 1][1], tt);
}
tt = dp[ans][ll][rr][1] + l - (x[n - rr + 1] - x[ll + 1]);
if (tt <= t[ll + 1])
{
dp[ans + 1][ll + 1][rr][0] = min(dp[ans + 1][ll + 1][rr][0], tt);
}
else
{
dp[ans][ll + 1][rr][0] = min(dp[ans][ll + 1][rr][0], tt);
}
}
}
}
}
// cerr << dp[5][0][5][1] << '\n';
cout << gans;
return 0;
}
