#include <bits/stdc++.h>
using namespace std;

int main() {
    int n, h;
    cin >> n >> h;
    vector<long long> a(n + 1), b(n + 1);
    for (int i = 1; i <= n; i++) {
        cin >> a[i];
    }
    for (int i = 1; i <= n; i++) {
        cin >> b[i];
    }
    vector<long long> s(n + 1);
    for (int i = 1; i <= n; i++) {
        s[i] = s[i - 1] + b[i];
    }
    int r = 0;
    long long ans = 0LL, sat = 0LL, fat = 0LL;
    for (int l = 1; l <= n; l++) {
        //cout << "l = " << l << endl;
        if (l >= 2) {
            sat -= a[l - 1];
            fat -= s[r] - s[l - 2];
        }
        //cout << r << " " << sat << " " << fat << endl;
        while (r <= n && fat <= h) {
            r++;
            sat += a[r];
            fat += (long long)(r - l + 1) * b[r];
        }
        //cout << r << " " << sat << " " << fat << endl;
        ans = max(ans, sat - a[r]);
    }
    cout << ans << endl;
}