#include <iostream>
#include <map>
using namespace std;
int n, l, x[205], t[205], late = -1;
map<int, int> dp[205][205];
int dist(int x1, int x2) {
if (x1 > x2) swap(x1, x2);
return min(x2 - x1, l - x2 + x1);
}
int solve(int i, int j, int time_passed) {
if (abs(i - j) == 1) return 0;
if (dp[i][j].count(time_passed)) return dp[i][j][time_passed];
int cur = i, l = min(i, j), r = max(i, j);
int ans = solve(l + 1, r, min(late, dist(x[cur], x[l + 1]) + time_passed)) + (dist(x[cur], x[l + 1]) + time_passed <= t[l + 1]);
ans = max(ans, solve(r - 1, l, min(late, dist(x[cur], x[r - 1]) + time_passed)) + (dist(x[cur], x[r - 1]) + time_passed <= t[r - 1]));
dp[i][j][time_passed] = ans;
return ans;
}
int main() {
cin >> n >> l;
for (int i = 1; i <= n; i++) {
cin >> x[i];
}
for (int i = 1; i <= n; i++) {
cin >> t[i];
late = max(late, t[i] + 1);
}
cout << solve(0, n + 1, 0) << '\n';
return 0;
}
