#include <bits/stdc++.h>
using namespace std;
int main(){
  int N, H;
  cin >> N >> H;
  vector<int> A(N);
  for (int i = 0; i < N; i++){
    cin >> A[i];
  }
  vector<int> B(N);
  for (int i = 0; i < N; i++){
    cin >> B[i];
  }
  vector<long long> S(N + 1);
  S[0] = 0;
  for (int i = 0; i < N; i++){
    S[i + 1] = S[i] + B[i];
  }
  int L = 0, R = 0;
  long long sum1 = 0, sum2 = 0;
  long long ans = 0;
  while (true){
    if (sum2 <= H){
      ans = max(ans, sum1);
      if (R == N){
        break;
      }
      sum1 += A[R];
      sum2 += (long long) (R - L + 1) * B[R];
      R++;
    } else {
      sum1 -= A[L];
      sum2 -= S[R] - S[L];
      L++;
    }
  }
  cout << ans << endl;
}