#include<bits/stdc++.h>
using namespace std;
//#pragma GCC optimize("Ofast")

#define rep(i,n) for(ll i=0;i<n;i++)
#define repl(i,l,r) for(ll i=(l);i<(r);i++)
#define per(i,n) for(ll i=(n)-1;i>=0;i--)
#define perl(i,r,l) for(ll i=r-1;i>=l;i--)
#define fi first
#define se second
#define pb push_back
#define ins insert
#define pqueue(x) priority_queue<x,vector<x>,greater<x>>
#define all(x) (x).begin(),(x).end()
#define CST(x) cout<<fixed<<setprecision(x)
#define vtpl(x,y,z) vector<tuple<x,y,z>>
#define rev(x) reverse(x);
using ll=long long;
using vl=vector<ll>;
using vvl=vector<vector<ll>>;
using pl=pair<ll,ll>;
using vpl=vector<pl>;
using vvpl=vector<vpl>;
const ll MOD=1000000007;
const ll MOD9=998244353;
const int inf=1e9+10;
const ll INF=4e18;
const ll dy[9]={1,0,-1,0,1,1,-1,-1,0};
const ll dx[9]={0,1,0,-1,1,-1,1,-1,0};
template<class T> inline bool chmin(T& a, T b) {
    if (a >= b) {
        a = b;
        return true;
    }
    return false;
}
template<class T> inline bool chmax(T& a, T b) {
    if (a < b) {
        a = b;
        return true;
    }
    return false;
}

int main(){
    ll n,h;cin >> n >> h;
    vl a(n),b(n);
    rep(i,n)cin >> a[i];
    rep(i,n)cin >> b[i];
    vl ca(n+1);rep(i,n)ca[i+1]=ca[i]+a[i];
    vl cb(n+1);rep(i,n)cb[i+1]=cb[i]+b[i]*(i+1);
    vl ncb(n+1);rep(i,n)ncb[i+1]=ncb[i]+b[i];
    ll ans=0;
    rep(i,n){
        ll ok=i,ng=n+1;
        while(ng-ok>1){
            ll mid=(ok+ng)/2;
            ll p=(cb[mid]-cb[i])-(ncb[mid]-ncb[i])*i;
            if(p<=h)ok=mid;
            else ng=mid;
        }
        chmax(ans,ca[ok]-ca[i]);
    }
    cout << ans << endl;
}