#define rep(i,n) for(int i=0;i<(int)(n);i++)
#define ALL(v) v.begin(),v.end()
typedef long long ll;
 
#include<bits/stdc++.h>
using namespace std;
 
int main(){
  ios::sync_with_stdio(false);
  std::cin.tie(nullptr);
  
  ll n,h;
  cin>>n>>h;
  vector<ll> A(n+1),B(n+1);
  rep(i,n) cin>>A[i+1];
  rep(i,n) cin>>B[i+1];
  vector<ll> S(n+2),SB(n+2);
  rep(i,n+1) S[i+1]=S[i]+A[i];
  rep(i,n+1) SB[i+1]=SB[i]+B[i];
  
  ll ma=0,r=0,tmp=0;
  rep(l,n+1){
    while(r+1<n+1 && tmp+(r-l+1)*B[r+1]<=h){
      r++;
      tmp+=(r-l+1)*B[r];
    }

    if(tmp<=h) ma=max(ma,S[r+1]-S[l]);

    if(r==l){
      ++r;
      if(r>=n+1) break;
      tmp+=B[r];
    }
    else tmp-=SB[r+1]-SB[l];
  }
  cout<<ma<<endl;
  
  return 0;
}