#include <bits/stdc++.h>
using namespace std;

int main() {
  int N, H, R = 0; cin >> N >> H;
  long long Ans = 0, Sum = 0, Tot = 0;
  vector<int> A(N), B(N);
  for (int &a : A) cin >> a;
  for (int &b : B) cin >> b;
  vector<long long> S(1);
  for (int i = 0; i < N; i++) S.push_back(S.at(i) + A.at(i));

  for (int L = 0; L < N; L++) {
    while(R < N && Sum + (R - L + 1) * B.at(R) <= H) {
      Sum += (R - L + 1) * B.at(R);
      Tot += B.at(R);
      R++;
    }
    Ans = max(Ans, S.at(R) - S.at(L));
    if (R == L) R++;
    else { Sum -= Tot; Tot -= B.at(L); }
  }

  cout << Ans << endl;
}