#include <bits/stdc++.h>
using namespace std;
constexpr int N = 205;
constexpr int inf = 1e9;
int a[N], t[N];
int dp[N][N][N][2];
int main() {
ios::sync_with_stdio(false);
cin.tie(nullptr);
int n, l;
cin >> n >> l;
for (int i = 1; i <= n; i++) {
cin >> a[i];
}
for (int i = 1; i <= n; i++) {
cin >> t[i];
}
for (int i = 0; i < N; i++) {
for (int j = 0; j < N; j++) {
for (int k = 0; k < N; k++) {
for (int s = 0; s < 2; s++) {
dp[i][j][k][s] = inf;
}
}
}
}
auto get = [&](int x, int y) {
int d = abs(x - y);
return min(d, l - d);
};
dp[0][0][0][0] = dp[0][0][0][1] = 0;
for (int i = 0; i <= n; i++) {
for (int j = 0; j <= n; j++) {
if (i + j >= n) continue;
for (int k = 0; k <= i + j; k++) {
vector<array<int, 2>> v;
v.push_back({dp[i][j][k][0], a[n - i + 1]});
v.push_back({dp[i][j][k][1], a[j]});
for (auto [time, pos] : v) {
int cnt = k, dist = get(pos, a[j + 1]);
if (time + dist <= t[j + 1]) {
cnt++;
}
dp[i][j + 1][cnt][1] = min(dp[i][j + 1][cnt][1], time + dist);
cnt = k; dist = get(pos, a[n - i]);
if (time + dist <= t[n - i]) {
cnt++;
}
dp[i + 1][j][cnt][0] = min(dp[i + 1][j][cnt][0], time + dist);
}
}
}
}
int ans = 0;
for (int i = 0; i <= n; i++) {
for (int j = 0; j <= n; j++) {
for (int k = 0; k <= n; k++) {
for (int s = 0; s < 2; s++) {
if (dp[i][j][k][s] != inf) {
ans = max(ans, k);
}
}
}
}
}
cout << ans << '\n';
return 0;
}
