#include <bits/stdc++.h>

using namespace std;

using i64 = long long;

#define yn(pope) (pope ? "Yes" : "No")

#define rep(i, n, m) for (int i = (n); i < (m); i++)
#define rrep(i, n, m) for (int i = (n); i > m; i--)

#define IINF (1 << 30)
#define INF (1ll << 60)

#define all(v) v.begin(), v.end()

int main() {
  int N;
  i64 H;
  cin >> N >> H;

  vector A(N + 1, 0ll), B(N + 1, 0ll);

  rep(i, 1, N + 1) { cin >> A[i]; }
  rep(i, 1, N + 1) { cin >> B[i]; }

  vector sum1(N + 1, 0ll);
  vector sum2(N + 1, 0ll);

  rep(i, 1, N + 1) { sum1[i] = sum1[i - 1] + A[i]; }
  rep(i, 1, N + 1) { sum2[i] = sum2[i - 1] + B[i]; }
  
  int l = 1, r = 1;
  i64 ans = 0, rem = 0;

  while (l < N) {
    if (r == N + 1 || rem > H) {
      rem -= sum2[r - 1] - sum2[l - 1];
      l++;
    } else {
      rem += (r - l + 1) * B[r];
      r++;
    }

    if (rem <= H) { ans = max(ans, sum1[r - 1] - sum1[l - 1]); }
  }

  cout << ans << endl;

  return 0;
}