#include<bits/stdc++.h>
typedef long long ll;
#define pii pair<ll, ll>
#define fi first
#define se second
#define endl '\n'
#define TASK ""
#define N 200005
#define LOG 17
using namespace std;
bool ghuy4g;
const ll inf = 1e16;
ll n, L;
pii a[N];
ll dis(ll i, ll j) {
if (i > j) swap(i, j);
if (j == n + 1) {
return min(a[i].fi, L - a[i].fi);
}
return min(a[j].fi - a[i].fi, L - a[j].fi + a[i].fi);
}
ll dp[205][205][205][2];
void solve() {
a[n + 1].fi = 0;
for (int i = 0; i <= n + 1; i ++) {
for (int j = 0; j <= n + 1; j ++) {
for (int z = 0; z <= n + 1; z ++) {
for (int t = 0; t < 2; t ++) {
dp[i][j][z][t] = inf;
}
}
}
}
ll ans = 0;
dp[0][0][0][0] = dp[0][0][0][1] = 0;
dp[0][n + 1][0][0] = dp[0][n + 1][0][1] = 0;
for (int i = 0; i <= n; i ++) {
for (int j = n + 1; j >= 1; j --) {
if (j <= i) continue;
for (int cnt = 1; cnt <= n; cnt ++) {
if (i > 0) dp[i][j][cnt][0] = min(dp[i][j][cnt][0], dp[i - 1][j][cnt][0] + dis(i, i - 1));
if (i > 0) dp[i][j][cnt][0] = min(dp[i][j][cnt][0], dp[i - 1][j][cnt][1] + dis(i, j));
if (j <= n) dp[i][j][cnt][1] = min(dp[i][j][cnt][1], dp[i][j + 1][cnt][0] + dis(i, j));
if (j <= n) dp[i][j][cnt][1] = min(dp[i][j][cnt][1], dp[i][j + 1][cnt][1] + dis(j + 1, j));
if (i > 0) {
ll xet = dp[i - 1][j][cnt - 1][0] + dis(i - 1, i);
xet = min(xet, dp[i - 1][j][cnt - 1][1] + dis(j, i));
//dp[i][j][cnt][0] = min(dp[i][j][cnt][0], xet);
if (xet <= a[i].se) {
dp[i][j][cnt][0] = min(dp[i][j][cnt][0], xet);
}
}
if (j <= n) {
ll xet = dp[i][j + 1][cnt - 1][1] + dis(j + 1, j);
xet = min(xet, dp[i][j + 1][cnt - 1][0] + dis(i, j));
if (xet <= a[j].se) {
dp[i][j][cnt][1] = min(dp[i][j][cnt][1], xet);
}
}
if (dp[i][j][cnt][0] <= a[i].se || dp[i][j][cnt][1] <= a[j].se) {
ans = max(ans, (ll)cnt);
}
}
}
}
cout << ans << endl;
}
bool klinh;
signed main() {
// freopen("test.inp", "r", stdin);
//freopen("test.out", "w", stdout);
//srand(time(0));
ios_base::sync_with_stdio(0);
cin.tie(0);
cin >> n >> L;
for (int i = 1; i <= n; i ++) {
cin >> a[i].fi;
}
for (int i = 1; i <= n; i ++) {
cin >> a[i].se;
}
sort(a + 1, a + 1 + n);
solve();
cerr << fabs(&klinh - &ghuy4g) / double(1024 * 1024);
}
