#include <bits/stdc++.h>
#define SORT(a) sort(a.begin(), a.end())
#define RSORT(a) sort(a.rbegin(), a.rend())
#define REP(i, n) for (int i = 0; i < n; i++)
#define RREP(i, n) for (int i = n - 1; 0 <= i; i--)
#define FOR(i, start, end) for (long long i = start; i < end; i++)
#define RFOR(i, start, end) for (long long i = start - 1; 0 <= i; i--)
#define ALL(a) a.begin(), a.end()
using ll = long long;
using namespace std;
constexpr int INF32       = 1'050'000'000;
constexpr long long INF64 = 4'000'000'000'000'000'000;
constexpr int MOD7        = 1'000'000'007;
constexpr int MOD9        = 1'000'000'009;
template <class T> inline bool chmin(T &a, T b) {
    if (a > b) {
        a = b;
        return true;
    }
    return false;
}
template <class T> inline bool chmax(T &a, T b) {
    if (a < b) {
        a = b;
        return true;
    }
    return false;
}
void print() { std::cout << '\n'; }
template <class H, class... T> void print(H &&head, T &&... args) {
    std::cout << head;
    sizeof...(args) == 0 ? std::cout << "" : std::cout << ' ';
    print(std::forward<T>(args)...);
}
template <class T> void print(std::vector<T> &v) {
    for (int i = 0; i < v.size(); i++) {
        std::cout << v[i];
        i == v.size() - 1 ? std::cout << '\n' : std::cout << ' ';
    }
}
template <class T> void print(std::vector<std::vector<T>> &v) {
    for (int i = 0; i < v.size(); i++) {
        for (int j = 0; j < v[i].size(); j++) {
            std::cout << v[i][j];
            j == v[i].size() - 1 ? std::cout << '\n' : std::cout << ' ';
        }
    }
}
void scan() {}
template <class H, class... T> void scan(H &&head, T &&... args) {
    std::cin >> head;
    scan(std::forward<T>(args)...);
}
template <class T> void scan(std::vector<T> &v) {
    for (auto &&i : v) {
        scan(i);
    }
}
template <class T> T up(T a, T div) { return (a + div - 1) / div; }

void debug() { std::cerr << '\n'; }
template <class H, class... T> void debug(H &&head, T &&... args) {
    std::cerr << head;
    sizeof...(args) == 0 ? std::cerr << "" : std::cerr << ' ';
    debug(std::forward<T>(args)...);
}
template <class T> void debug(std::vector<T> &v) {
    for (int i = 0; i < v.size(); i++) {
        std::cerr << v[i];
        i == v.size() - 1 ? std::cerr << '\n' : std::cerr << ' ';
    }
}
template <class T> void debug(std::vector<std::vector<T>> &v) {
    for (int i = 0; i < v.size(); i++) {
        for (int j = 0; j < v[i].size(); j++) {
            std::cerr << v[i][j];
            j == v[i].size() - 1 ? std::cerr << '\n' : std::cerr << ' ';
        }
    }
}

int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);

    ll N, K;
    scan(N, K);
    vector<ll> A(N), F(N);
    scan(A);
    scan(F);

    SORT(A);
    RSORT(F);

    auto check = [&](ll x) {
        ll cnt = 0;
        REP(i, N) { cnt += max(A[i] - x / F[i], 0LL); }
        return cnt <= K;
    };

    ll r = 1E12 + 1;
    ll l = 0;
    // ll ans = INF64;

    auto binarySearch = [](auto left, auto right, auto comp) {
        auto ret = right;
        left--;
        while (1 < right - left) {
            auto mid = (left + right) / 2;
            if (comp(mid)) {
                right = mid;
                ret   = mid;
            } else {
                left = mid;
            }
        }
        return ret;
    };
    auto ans = binarySearch(l, r, [&](ll x) {
        ll cnt = 0;
        REP(i, N) { cnt += max(A[i] - x / F[i], 0LL); }
        return cnt <= K;
    });
    // while (l < r) {
    //     ll mid = (l + r) / 2;
    //     ll cnt = 0;
    //     REP(i, N) cnt += max(A[i] - mid / F[i], 0LL);
    //     if (cnt <= K) {
    //         r   = mid;
    //         ans = mid;
    //     } else {
    //         l = mid + 1;
    //     }
    // }
    debug(r, l);
    print(ans);

    return 0;
}

Measured memory_bytes: 3328