#include <bits/stdc++.h>
using namespace std;
const int N = 202, T = 1000000000;
int x[N], t[N], early[N][N][N][2];
void set_min(int &a, int b) {
a = min(a, b);
}
int main() {
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
int n, c;
cin >> n >> c;
for (int i = 1; i <= n; ++i) {
cin >> x[i];
}
x[n + 1] = c;
for (int i = 0; i < n; ++i) {
cin >> t[i];
}
for (int l = 0; l <= n; ++l) {
for (int r = 0; r <= n; ++r) {
for (int i = 0; i <= n; ++i) {
for (int j = 0; j < 2; ++j) {
early[l][r][i][j] = T + 1;
}
}
}
}
early[0][0][0][0] = early[0][0][0][1] = 0;
for (int i = 0; i < n; ++i) {
for (int l = 0; l <= i; ++l) {
int r = i - l, s;
for (int j = 0; j <= i; ++j) {
if (early[l][r][j][0] <= T) {
s = early[l][r][j][0] + x[l + 1] - x[l];
set_min(early[l + 1][r][j + (s <= t[l])][0], s);
s = early[l][r][j][0] + x[l] + c - x[n - r];
set_min(early[l][r + 1][j + (s <= t[n - 1 - r])][1], s);
}
if (early[l][r][j][1] <= T) {
s = early[l][r][j][1] + x[l + 1] + c - x[n + 1 - r];
set_min(early[l + 1][r][j + (s <= t[l])][0], s);
s = early[l][r][j][1] + x[n + 1 - r] - x[n - r];
set_min(early[l][r + 1][j + (s <= t[n - 1 - r])][1], s);
}
}
}
}
int ans = 0;
for (int l = 0; l <= n; ++l) {
int r = n - l;
for (int i = 0; i <= n; ++i) {
for (int j = 0; j < 2; ++j) {
if (early[l][r][i][j] <= T) {
ans = max(ans, i);
}
}
}
}
cout << ans << "\n";
}
