#include <stdio.h>
#include <atcoder/all>
#include <bits/stdc++.h>
using namespace std;
using namespace atcoder;
using mint = modint998244353;
#define rep(i,n) for (int i = 0; i < (n); ++i)
#define Inf32 1000000001
#define Inf64 1000000000000000001

int main(){
	
	ios::sync_with_stdio(false);
	std::cin.tie(nullptr);
	
	long long N,H;
	cin>>N>>H;
	vector<long long> a(N),b(N);
	rep(i,N)cin>>a[i];
	rep(i,N)cin>>b[i];
	long long ans = 0;
	long long as = 0;
	long long bs = 0;
	long long cs = 0;
	int l = -1;
	rep(i,N){
		bs += b[i];
		cs += b[i] * (i-l);
		as += a[i];
		while(cs > H){
			cs -= bs;
			bs -= b[l+1];
			as -= a[l+1];
			l++;
		}
		ans = max(ans,as);
	}
	cout<<ans<<endl;
	return 0;
}