#include <bits/stdc++.h>

using namespace std;
using ll = long long;

int main(){
    cin.tie(nullptr);
    ios_base::sync_with_stdio(false);

    ll N, H, ans=0;
    cin >> N >> H;
    vector<ll> A(N+1), B(N+1), SA(N+1), SB(N+1), SC(N+1);
    for (int i=1; i<=N; i++){
        cin >> A[i];
        SA[i] = SA[i-1] + A[i];
    }
    for (int i=1; i<=N; i++){
        cin >> B[i];
        SB[i] = SB[i-1] + B[i];
        SC[i] = SC[i-1] + B[i]*i;
    }

    for (int i=1; i<=N; i++){
        if (B[i] > H) continue;
        ll ok=i, ng=N+1;
        while (ng-ok > 1){
            ll mid = (ok+ng)/2;
            if (SC[mid] - SC[i-1] - (SB[mid]-SB[i-1]) * (i-1) <= H){
                ok = mid;
            } else {
                ng = mid;
            }
        }
        //cout << i << " " << ok << " " << SC[ok] - SC[i-1] - (SB[ok]-SB[i-1]) *(i-1) << " " <<  SA[ok]-SA[i-1] << endl;
        ans = max(ans, SA[ok]-SA[i-1]);
    }

    cout << ans << endl;

    return 0;
}