#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define int ll
using P = pair<int, int>;
#define all(x) x.begin(), x.end()
#define rep(i, l, n) for (int i = l; i < (n); ++i)
#define sz(x) (int)x.size()
const char nl = '\n';
const int mod = 998244353;
const int inf = 1e9+10;
void mnu(int &a, int b) {
if (b < a)a = b;
}
void solve() {
int n, l; cin >> n >> l;
vector<int> a(1, 0), t(n+1);
rep(i, 0, n) {
int x; cin >> x;
a.push_back(x);
}
//vector<int>
rep(i, 1, n+1)cin >> t[i];
vector<int> b(1, 0);
for (int i = n; i >= 1; --i)b.push_back(a[i]);
int dp[n+1][n+1][2][n+1];
rep(i, 0, n+1)
rep(j, 0, n+1)
rep(w, 0, 2)
rep(cnt, 0, n+1)
dp[i][j][w][cnt] = inf;
rep(i, 1, n+1) {
if (l-b[i] <= t[n-i+1])dp[0][i][0][1] = dp[0][i][1][1] = l-b[i];
if (a[i] <= t[i])dp[i][0][1][1] = dp[i][0][0][1] = a[i];
}
b[0] = l;
rep(i, 0, n+1) {
rep(j, 0, n+1) {
if (n < i+j || i+j==0)continue;
rep(cnt, 1, n+1) {
if (i)
mnu(dp[i][j][1][cnt], dp[i-1][j][1][cnt]);
if (j)
mnu(dp[i][j][0][cnt], dp[i][j-1][0][cnt]);
if (i) {
if (dp[i-1][j][0][cnt-1]+a[i]-a[i-1] <= t[i])mnu(dp[i][j][0][cnt], dp[i-1][j][0][cnt-1]+a[i]-a[i-1]);
if (dp[i-1][j][1][cnt-1]+l-b[j]+a[i] <= t[i])mnu(dp[i][j][0][cnt], dp[i-1][j][1][cnt-1]+l-b[j]+a[i]);
}
if (j) {
if (dp[i][j-1][0][cnt-1]+a[i]+l-b[j] <= t[n-j+1])mnu(dp[i][j][1][cnt], dp[i][j-1][0][cnt-1]+a[i]+l-b[j]);
if (dp[i][j-1][1][cnt-1]+b[j-1]-b[j] <= t[n-j+1])mnu(dp[i][j][1][cnt], dp[i][j-1][1][cnt-1]+b[j-1]-b[j]);
}
}
}
}
int res = 0;
rep(i, 0, n+1)
rep(j, 0, n+1)
rep(cnt, 1, n+1) {
if (dp[i][j][0][cnt] != inf) {
res = max(res, cnt);
}
if (dp[i][j][1][cnt] != inf) {
res = max(res, cnt);
}
}
cout << res << nl;
}
int32_t main() {
ios_base::sync_with_stdio(0);
cin.tie(0);
solve();
return 0;
}
