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

#define FOR(i, a, b) for(int i=(a);i<(b);++i)
#define REP(i, n)  for(int i=0;i<(n);++i)
#define REPr(i, n) for(int i=(n)-1;i>=0; --i)
#define FORq(i, m, n) for(int i = (m);i <= (n);++i)
#define FORqr(i, m, n) for(int i = (n);i >=(m);--i)
#define PB push_back
#define MP make_pair
#define fst first
#define snd second
#define SIN(x, S) (S.count(x) != 0)
#define M0(x) memset(x,0,sizeof(x))
#define FILL(x, y) memset(x,y,sizeof(x))
#define MM(x) memset(x,-1,sizeof(x))
#define ALL(x) (x).begin(),(x).end()
#define DB(x) cerr << #x << " = " << x << endl
#define DB2(x, y) cerr << "(" << #x << ", " << #y << ") = (" << x << ", " << y << ")\n";
#define DEBUG int x12345; cin >> x12345;
typedef pair<int, int> PII;
typedef pair<long long, long long> PLL;
typedef vector<int> VI;
typedef vector<VI> VVI;
typedef vector<long long> VL;
typedef long long ll;
typedef long long integer;
///////////////////////////////////////////////
const ll MOD = 1e9 + 7;
ll gcd(ll x, ll y) { return y ? gcd(y, x % y) : x; }

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;
}

template<int MOD>
struct Fp {
    long long val;

    constexpr Fp(long long v = 0) noexcept : val(v % MOD) {
        if (val < 0) v += MOD;
    }

    constexpr int getmod() { return MOD; }

    constexpr Fp operator-() const noexcept {
        return val ? MOD - val : 0;
    }

    constexpr Fp operator+(const Fp &r) const noexcept { return Fp(*this) += r; }

    constexpr Fp operator-(const Fp &r) const noexcept { return Fp(*this) -= r; }

    constexpr Fp operator*(const Fp &r) const noexcept { return Fp(*this) *= r; }

    constexpr Fp operator/(const Fp &r) const noexcept { return Fp(*this) /= r; }

    constexpr Fp &operator+=(const Fp &r) noexcept {
        val += r.val;
        if (val >= MOD) val -= MOD;
        return *this;
    }

    constexpr Fp &operator-=(const Fp &r) noexcept {
        val -= r.val;
        if (val < 0) val += MOD;
        return *this;
    }

    constexpr Fp &operator*=(const Fp &r) noexcept {
        val = val * r.val % MOD;
        return *this;
    }

    constexpr Fp &operator/=(const Fp &r) noexcept {
        long long a = r.val, b = MOD, u = 1, v = 0;
        while (b) {
            long long t = a / b;
            a -= t * b;
            swap(a, b);
            u -= t * v;
            swap(u, v);
        }
        val = val * u % MOD;
        if (val < 0) val += MOD;
        return *this;
    }

    constexpr bool operator==(const Fp &r) const noexcept {
        return this->val == r.val;
    }

    constexpr bool operator!=(const Fp &r) const noexcept {
        return this->val != r.val;
    }

    friend constexpr ostream &operator<<(ostream &os, const Fp<MOD> &x) noexcept {
        return os << x.val;
    }

    friend constexpr istream &operator>>(istream &is, Fp<MOD> &x) noexcept {
        return is >> x.val;
    }

    friend constexpr Fp<MOD> modpow(const Fp<MOD> &a, long long n) noexcept {
        if (n == 0) return 1;
        auto t = modpow(a, n / 2);
        t = t * t;
        if (n & 1) t = t * a;
        return t;
    }
};

using mint = Fp<MOD>;

void scdvec(vector<int> &a, int n, int s = 0) {
    for (int i = s; i < n; ++i) { scanf("%d", &a[i]); }
}

void sclldvec(vector<long long> &a, int n, int s = 0) {
    for (int i = s; i < n; ++i) { scanf("%lld", &a[i]); }
}

///////////////////////////////////////////////
///  ((((っ・ω・)っ |AC|
ll N, K;
vector<ll> A, F;
bool check(ll target) {
    ll rest = K;
    REP(i, N) {
        ll a, f;
        a = A[i];
        f = F[i];
        if (a * f <= target) continue;
        ll change = target / f;
        rest -= (A[i] - change);
    }
    if (rest >= 0) return true;
    else return false;
}
#define int long long
template<class F> int binary(int ok, int ng, F f) {
    while (abs(ok - ng) > 1) {
        int mid = (ok + ng) / 2;
        if (f(mid)) {
            ok = mid;
        } else {
            ng = mid;
        }
    }
    return ok;
}

signed main() {
    int N, K;
    cin >> N >> K;
    vector<int> A(N), B(N);
    REP(i, N) {
        cin >> A[i];
    }
    REP(i, N) {
        cin >> B[i];
    }
    sort(A.begin(), A.end());
    sort(B.rbegin(), B.rend());
    auto f = [&](int v) {
        int k = K;
        REP(i, N) {
            int need = v / B[i];
            k -= max(0ll, A[i] - need);
        }
        return k >= 0;
    };
    cout << binary(1e18 + 10, -1, f) << endl;

    return 0;
}

Measured memory_bytes: 3328