#include <bits/stdc++.h>
using namespace std;
#define all(v) (v).begin(), (v).end()
using ll = long long;
using ld = long double;
using pint = pair<int, int>;
using pll = pair<ll, ll>;

int main() {
    int N, H; cin >> N >> H;
    vector<ll> A(N), B(N), SA(N+1, 0), SB(N+1, 0);
    for (int i = 0; i < N; i++) {
        cin >> A[i];
        SA[i+1] = SA[i] + A[i];
    }
    for (int i = 0; i < N; i++) {
        cin >> B[i];
        SB[i+1] = SB[i] + B[i];
    }
    ll ans = 0, hval = 0;
    for (int l = 0, r = 0; l < N; l++) {
        while (r < N && hval + (r - l + 1)*B[r] <= H) {
            hval += (r - l + 1)*B[r];
            r++;
        }
        ans = max(SA[r] - SA[l], ans);
        hval -= SB[r] - SB[l];
    }
    cout << ans << endl;
}