#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
#define rep(i, n) for(int i=0;i<(n);++i)
#define rep1(i, n) for(int i=1;i<=(n);i++)
#define ll long long
using mint = modint998244353;
using P = pair<ll,ll>;
using lb = long double;
using T = tuple<ll, ll, ll>;
#ifdef LOCAL
#  include <debug_print.hpp>
#  define dbg(...) debug_print::multi_print(#__VA_ARGS__, __VA_ARGS__)
#else
#  define dbg(...) (static_cast<void>(0))
#endif

int main()
{
    int n, h;
    cin >> n >> h;
    vector<ll> a(n), b(n);
    rep(i,n) cin >> a[i];
    rep(i,n) cin >> b[i];
    vector<ll> sum(n+1);
    vector<ll> S(n+1);
    vector<ll> msum(n+1);
    rep(i,n) S[i+1] = S[i] + a[i];
    rep(i,n) sum[i+1] = sum[i] + b[i];
    rep(i,n) msum[i+1] = msum[i] + (i+1) * b[i];
    int j = 0;
    ll ans = 0;
    for(int i=0;i<n;i++){
        while(j<n){
            ll now = msum[j+1] - msum[i] - i*(sum[j+1]-sum[i]);
            if(now>h) break;
            else {
                ans = max(ans, S[j+1]-S[i]);
                dbg(i, j, S[j+1]-S[i]);
                dbg(now);
                j++;
            }
        }
    }
    cout << ans << endl;
    return 0;
}