#include <iostream>
#include <vector>
#include <queue>
#include <tuple>
using namespace std;
const int INF = (int)1e9 + 1;
const int N = 205;
int n, l, x[N], t[N], dp[N][N][N];
int dist(int x1, int x2) {
if (x1 > x2) swap(x1, x2);
return min(x2 - x1, l - x2 + x1);
}
int solve() {
for (int i = 0; i < N; i++) {
for (int j = 0; j < N; j++) {
for (int k = 0; k < N; k++) {
dp[i][j][k] = -INF;
}
}
}
int ans = 0;
priority_queue<tuple<int, int, int, int>> pq;
dp[0][n + 1][0] = 0;
pq.push({0, 0, n + 1, 0});
while (not pq.empty()) {
int d, i, j, c;
tie(d, i, j, c) = pq.top();
ans = max(ans, c);
pq.pop();
if (dp[i][j][c] != d or abs(i - j) == 1) continue;
int cur = i, l = min(i, j), r = max(i, j);
{
// cur -> l + 1
int d_nxt = min(INF, dist(x[cur], x[l + 1]) - d);
int c_nxt = (d_nxt <= t[l + 1]) + c;
if (dp[l + 1][r][c_nxt] < -d_nxt) {
dp[l + 1][r][c_nxt] = -d_nxt;
pq.push({-d_nxt, l + 1, r, c_nxt});
}
}
{
// cur -> r - 1
int d_nxt = min(INF, dist(x[cur], x[r - 1]) - d);
int c_nxt = (d_nxt <= t[r - 1]) + c;
if (dp[r - 1][l][c_nxt] < -d_nxt) {
dp[r - 1][l][c_nxt] = -d_nxt;
pq.push({-d_nxt, r - 1, l, c_nxt});
}
}
}
return ans;
}
int main() {
cin >> n >> l;
x[0] = 0;
for (int i = 1; i <= n; i++) {
cin >> x[i];
}
for (int i = 1; i <= n; i++) {
cin >> t[i];
}
cout << solve() << '\n';
return 0;
}
