#include <bits/stdc++.h>
using namespace std;
#define FOR(i,m,n) for(int i=(m);i<(n);++i)
#define REP(i,n) FOR(i,0,n)
using ll = long long;
constexpr int INF = 0x3f3f3f3f;
constexpr long long LINF = 0x3f3f3f3f3f3f3f3fLL;
constexpr double EPS = 1e-8;
constexpr int MOD = 998244353;
// constexpr int MOD = 1000000007;
constexpr int DY4[]{1, 0, -1, 0}, DX4[]{0, -1, 0, 1};
constexpr int DY8[]{1, 1, 0, -1, -1, -1, 0, 1};
constexpr int DX8[]{0, -1, -1, -1, 0, 1, 1, 1};
template <typename T, typename U>
inline bool chmax(T& a, U b) { return a < b ? (a = b, true) : false; }
template <typename T, typename U>
inline bool chmin(T& a, U b) { return a > b ? (a = b, true) : false; }
struct IOSetup {
  IOSetup() {
    std::cin.tie(nullptr);
    std::ios_base::sync_with_stdio(false);
    std::cout << fixed << setprecision(20);
  }
} iosetup;

int main() {
  int n, h; cin >> n >> h;
  vector<int> a(n), b(n);
  for (int& a_i : a) cin >> a_i;
  for (int& b_i : b) cin >> b_i;
  vector<ll> sum1(n + 1, 0), sum2(n + 1, 0), sum3(n + 1, 0);
  REP(i, n) sum1[i + 1] = sum1[i] + a[i];
  REP(i, n) sum2[i + 1] = sum2[i] + b[i];
  REP(i, n) sum3[i + 1] = sum3[i] + b[i] * (i + 1LL);
  ll ans = 0;
  REP(i, n) {
    int l = i - 1, r = n;
    while (r - l > 1) {
      const int m = midpoint(l, r);
      (sum3[m + 1] - sum3[i] - (sum2[m + 1] - sum2[i]) * i <= h ? l : r) = m;
    }
    chmax(ans, sum1[l + 1] - sum1[i]);
  }
  cout << ans << '\n';
  return 0;
}