#include <bits/stdc++.h> using namespace std; #define int long long void solve() { int n, l; cin >> n >> l; vector <int> x(n), t(n); for (int i = 0; i < n; ++i) { cin >> x[i]; } for (int i = 0; i < n; ++i) { cin >> t[i]; } int ans = 0; int inf = 2e18; vector <vector <vector <int>>> dp(2, vector <vector <int>> (n + 1, vector <int> (n + 1, 2e18))); vector <vector <vector <int>>> last = dp; last[0][0][0] = 0; int st = 0; for (int i = 0; i <= n; ++i) { for (int j = 0; j <= n; ++j) { for (int f = 0; f + j < n; ++f) { if (last[0][j][f] != inf) { if (j == 0) { st = 0; } else { st = x[j - 1]; } if (x[j] - st + last[0][j][f] <= t[j]) { // cout << i << " " << j << " " << f << endl; dp[0][j + 1][f] = min(dp[0][j + 1][f], x[j] - st + last[0][j][f]); // cout << dp[0][j + 1][f] << endl; } int ind = n - 1 - f; // cout << i << " " << j << " " << f << endl; // cout << l << " " << x[ind] << " " << st << " " << last[0][j][f] << " " << t[ind] << endl; if (l - x[ind] + st + last[0][j][f] <= t[ind]) { dp[1][j][f + 1] = min(dp[1][j][f + 1], l - x[ind] + st + last[0][j][f]); } } if (last[1][j][f] != inf) { if (f == 0) { st = l; } else { st = x[n - f]; } if (last[1][j][f] + st - x[n - f - 1] <= t[n - f - 1]) { // cout << i << " " << " " << j << " " << f << endl; dp[1][j][f + 1] = min(dp[1][j][f + 1], last[1][j][f] + st - x[n - f - 1]); } if (last[1][j][f] + l - st + x[j] <= t[j]) { // cout << i << " " << " " << j << " " << f << endl; dp[0][j + 1][f] = min(dp[0][j + 1][f], last[1][j][f] + l - st + x[j]); } } } } for (int j = 0; j <= n; ++j) { for (int f = 0; f + j < n; ++f) { if (f == 0) { st = l; } else { st = x[n - f]; } dp[0][j + 1][f] = min(dp[0][j + 1][f], dp[1][j][f] + l - st + x[j]); dp[1][j][f + 1] = min(dp[1][j][f + 1], dp[1][j][f] + st - x[n - f - 1]); if (j == 0) { st = 0; } else { st = x[j - 1]; } dp[1][j][f + 1] = min(dp[1][j][f + 1], l - x[n - f - 1] + st + dp[0][j][f]); dp[0][j + 1][f] = min(dp[0][j + 1][f], x[j] - st + dp[0][j][f]); } } bool flag = false; for (int j = 0; j <= n; ++j) { for (int f = 0; f + j <= n; ++f) { if (dp[0][j][f] < inf || dp[1][j][f] < inf) { flag = true; } last[0][j][f] = inf; last[1][j][f] = inf; } } swap(last, dp); if (flag) { ans = i + 1; } else { break; } } cout << ans << '\n'; } signed main() { cin.tie(0); ios::sync_with_stdio(false); solve(); } /* 4 19 3 7 12 14 2 0 5 4 */