#include <iostream>
#include <vector>
#include <set>
#include <map>
#include <algorithm>
#include <functional>
#include <queue>
using namespace std;
const int inf = 1e9 + 1;
const int maxn = 201;
int dp[maxn][maxn][maxn][2];
bool used[maxn][maxn][maxn][2];
int32_t main() {
ios_base::sync_with_stdio(false);
cin.tie(0);
cout.tie(0);
int n, l;
cin >> n >> l;
vector<int> x(n);
for (int& i : x) {
cin >> i;
}
vector<int> t(n);
for (int& i : t) {
cin >> i;
}
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][0] = dp[i][j][k][1] = inf;
}
}
}
auto dist = [&](int i, int j) {
return min(abs(x[i] - x[j]), l - max(x[i], x[j]) + min(x[i], x[j]));
};
auto d = [&] (int i) {
return min(x[i], l - x[i]);
};
priority_queue<pair<int, pair<pair<int, int>, pair<int, int>>>> q;
if (d(0) <= t[0]) {
dp[0][0][1][1] = d(0);
q.push({ -dp[0][0][1][1], { { 0, 0 }, { 1 , 1 } } });
} else {
dp[0][0][0][1] = d(0);
q.push({ -dp[0][0][0][1], { { 0, 0 }, { 0, 1 } } });
}
if (d(n - 1) <= t[n - 1]) {
dp[n - 1][n - 1][1][0] = d(n - 1);
q.push({ -dp[n - 1][n - 1][1][0], { { n - 1, n - 1 }, { 1, 0 } } });
} else {
dp[n - 1][n - 1][0][0] = d(n - 1);
q.push({ -dp[n - 1][n - 1][0][0], { { n - 1, n - 1 }, { 0, 0 } } });
}
while (!q.empty()) {
auto [a, b] = q.top().second;
auto [l, r] = a;
auto [c, s] = b;
q.pop();
if (used[l][r][c][s]) continue;
used[l][r][c][s] = 1;
if ((r + 1) % n == l) continue;
if (s) {
int rp = (r + 1) % n;
int tp = dp[l][r][c][s] + dist(r, rp);
int nc = c;
if (tp <= t[rp]) {
++nc;
}
if (tp < dp[l][rp][nc][s]) {
dp[l][rp][nc][s] = tp;
q.push({ -dp[l][rp][nc][s], { { l, rp }, { nc, s } } });
}
} else {
int lp = (l - 1 + n) % n;
int tp = dp[l][r][c][s] + dist(l, lp);
int nc = c;
if (tp <= t[lp]) {
++nc;
}
if (tp < dp[lp][r][nc][s]) {
dp[lp][r][nc][s] = tp;
q.push({ -dp[lp][r][nc][s], { { lp, r }, { nc, s } } });
}
}
if (dp[l][r][c][s ^ 1] > dp[l][r][c][s] + dist(l, r)) {
dp[l][r][c][s ^ 1] = dp[l][r][c][s] + dist(l, r);
q.push({ -dp[l][r][c][s ^ 1], { { l, r }, { c, s ^ 1 } } });
}
}
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 q = 0; q < 2; ++q) {
if (dp[i][j][k][q] < inf) {
ans = max(ans, k);
}
}
}
}
}
cout << ans;
}
