#include<bits/stdc++.h>
// #include<atcoder/all>
// #include<boost/multiprecision/cpp_int.hpp>

using namespace std;
// using namespace atcoder;
// using bint = boost::multiprecision::cpp_int;
using ll = long long;
using ull = unsigned long long;
using P = pair<int,int>;
using vi = vector<ll>;
using vvi = vector<vi>;
using vvvi = vector<vvi>;
#define rep(i,n) for(ll i = 0;i < (ll)n;i++)
#define ALL(x) (x).begin(),(x).end()
#define sz(c) ((ll)(c).size())
#define LB(A,x) (int)(lower_bound(A.begin(),A.end(),x)-A.begin())
// #define MOD 1000000007
#define MOD 998244353
template<typename T>using min_priority_queue=priority_queue<T,vector<T>,greater<T>>;
template<typename T>ostream&operator<<(ostream&os,vector<T>&v){for(int i = 0;i < v.size();i++)os<<v[i]<<(i+1!=v.size()?" ":"");return os;}
template<typename T>istream&operator>>(istream&is,vector<T>&v){for(T&in:v)is>>in;return is;}
template<typename T1,typename T2>ostream&operator<<(ostream&os,pair<T1,T2>&p){os<<p.first<<" "<<p.second;return os;}
template<typename T1,typename T2>istream&operator>>(istream&is,pair<T1,T2>&p){is>>p.first>>p.second;return is;}



int main(){
  
  ios_base::sync_with_stdio(0), cin.tie(0);
  ll n,H;
  cin >> n >> H;
  vi a(n),b(n);
  cin >> a >> b;
  vi sa(n+1),sb(n+1);
  vector<__int128_t> ssb(n+1,0);
  rep(i,n)sa[i+1] = sa[i] + a[i];
  rep(i,n)sb[i+1] = sb[i] + b[i];
  rep(i,n)ssb[i+1] = ssb[i] + sb[i+1];
  ll res = 0;
  rep(i,n){
    ll l = 0,r = n-i+1;
    while(r-l > 1){
      ll mid = (l+r)/2;
      __int128_t k = ssb[i+mid]-ssb[i] - sb[i]*mid;
      if(k <= H)l = mid;
      else r = mid;
    }
    res = max(res,sa[i+l]-sa[i]);
  }
  cout << res << "\n";
  

  return 0;
}