#include <bits/stdc++.h>
using namespace std;
#include <atcoder/all>
using namespace atcoder;
using ll = long long;
using VI = vector<int>;
using VVI = vector<VI>;
using VL = vector<ll>;
using VVL = vector<VL>;
using VD = vector<double>;
using VVD = vector<VD>;
using VS = vector<string>;
using P = pair<ll,ll>;
using VP = vector<P>;
#define rep(i, n) for (ll i = 0; i < ll(n); i++)
#define out(x) cout << x << endl
#define dout(x) cout << fixed << setprecision(10) << x << endl
#define all(a) (a).begin(),(a).end()
#define rall(a) (a).rbegin(),(a).rend()
#define sz(x) (int)(x.size())
#define re0 return 0
#define pcnt __builtin_popcountll
template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }
constexpr int inf = 1e9;
constexpr ll INF = 1e18;
//using mint = modint1000000007;
using mint = modint998244353;
int di[4] = {1,0,-1,0};
int dj[4] = {0,1,0,-1};

int main(){
    ll n,h;
    cin >> n >> h;
    VL a(n),b(n),c(n);
    rep(i,n) cin >> a[i];
    rep(i,n) cin >> b[i];
    rep(i,n) c[i] = (i+1)*b[i];
    VL cmla(n+1),cmlb(n+1),cmlc(n+1);
    rep(i,n) cmla[i+1] = cmla[i]+a[i];
    rep(i,n) cmlb[i+1] = cmlb[i]+b[i];
    rep(i,n) cmlc[i+1] = cmlc[i]+c[i];
    ll ans = 0;
    rep(i,n){
        if(h < b[i]) continue;
        auto get = [&](ll x){
            ll res = cmlc[x]-cmlc[i];
            res -= i*(cmlb[x]-cmlb[i]);
            return res;
        };
        ll ok = i+1,ng = n+1;
        while(abs(ok-ng)>1){
            ll mid = (ok+ng)/2;
            if(get(mid) <= h) ok = mid;
            else ng = mid;
            //cout << i << ' ' << mid << ' ' << get(mid) << endl;
        }
        chmax(ans,cmla[ok]-cmla[i]);
    }
    out(ans);
}