#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using vll = vector<ll>;
#define rep(i, n) for (ll i = 0; i < (ll) (n); i++)
int main() {
    ll N,H;
    cin>>N>>H;
    ll an=0,P=0,Q=0;
    vll A(N),B(N),SB(N+1,0);
    rep(i,N)cin>>A[i];
    rep(i,N){
        cin>>B[i];
        SB[i+1]=SB[i]+B[i];
    }
    deque<ll> D;
    rep(i,N){
        D.push_back(i);
        P+=B[i]*D.size();
        Q+=A[i];
        while(P>H){
            Q-=A[D.front()];
            P-=SB[D.back()+1]-SB[D.front()];
            D.pop_front();
        }
        an=max(an,Q);
    }
    cout<<an<<endl;
}