#include<bits/stdc++.h>
using namespace std;
#include<atcoder/all>
using namespace atcoder;
#define rep(i,n) for (int i = 0; i < (n); ++i)
using ld = long double;
using ll = long long;

template<class T> bool chmax(T &a, T b)
{
	if(a<b)
	{
	a = b;
	return true;
	}
	return false;
}
template<class T> bool chmin(T &a, T b)
{
	if(a>b)
	{
		a = b;
		return true;
	}
	return false;
}

int N, H, A[1<<18], B[1<<18];
using P = pair<ll,ll>;

int main()
{
	cin >> N >> H;
	rep(i,N) cin >> A[i];
	rep(i,N) cin >> B[i];

	vector<ll> S(N+1);
	rep(i,N) S[i+1] = S[i]+B[i];

	deque<P> q;
	ll a = 0, b = 0, ans = 0;
	int l = 0;
	rep(i,N)
	{
		q.push_back({A[i], B[i]});
		a += A[i];
		b += B[i]*(ll)q.size();
		while(b>H && !q.empty())
		{
			auto [x,y] = q.front();
			q.pop_front();
			a -= x;
			b -= S[i+1]-S[l++];
		}
		//cout << a << " " << b << endl;
		chmax(ans, a);
	}
	cout << ans << endl;
}