//header
#define set_header 1
#ifdef set_header
    #pragma GCC optimize("Ofast")
    #include <bits/stdc++.h>
    #ifdef LOCAL
        #include "cxx-prettyprint-master/prettyprint.hpp"
        #define print(x) cout << x << endl
    #else
        #define print(...) 42
    #endif
    using namespace std;
    using ll = long long;
    #define INF 1'010'000'000'000'000'017LL
    #define mod 998244353LL
    #define eps 0.0001
    #define all(x) (x).begin(), (x).end()
    #define reverse(x) (x).rbegin(), (x).rend()
    #define FOR(i,a,b) for(ll i=(a);i<(b);++i)
    #define rep(i,n)  FOR(i,0,n)
    #define SZ(x) ((ll)(x).size())
    #define sum(x) accumulate(ALL(x), 0LL)//?
    #define pb(x) push_back(x)
    typedef pair < ll , ll >P;
    ll gcd(ll a, ll b) { return b ? gcd(b, a%b) : a; }
    template<class T>bool chmax(T &a, const T &b) { if (a<b) { a=b; return 1; } return 0; }
    template<class T>bool chmin(T &a, const T &b) { if (b<a) { a=b; return 1; } return 0; }
    template <std::uint_fast64_t Modulus> class modint {
        using u64 = std::uint_fast64_t;

        public:
        u64 a;

        constexpr modint(const u64 x = 0) noexcept : a(x % Modulus) {}
        constexpr u64 &value() noexcept { return a; }
        constexpr const u64 &value() const noexcept { return a; }
        constexpr modint operator+(const modint rhs) const noexcept {
            return modint(*this) += rhs;
        }
        constexpr modint operator-(const modint rhs) const noexcept {
            return modint(*this) -= rhs;
        }
        constexpr modint operator*(const modint rhs) const noexcept {
            return modint(*this) *= rhs;
        }
        constexpr modint operator/(const modint rhs) const noexcept {
            return modint(*this) /= rhs;
        }
        constexpr modint &operator+=(const modint rhs) noexcept {
            a += rhs.a;
            if (a >= Modulus) {
            a -= Modulus;
            }
            return *this;
        }
        constexpr modint &operator-=(const modint rhs) noexcept {
            if (a < rhs.a) {
            a += Modulus;
            }
            a -= rhs.a;
            return *this;
        }
        constexpr modint &operator*=(const modint rhs) noexcept {
            a = a * rhs.a % Modulus;
            return *this;
        }
        constexpr modint &operator/=(modint rhs) noexcept {
            u64 exp = Modulus - 2;
            while (exp) {
            if (exp % 2) {
                *this *= rhs;
            }
            rhs *= rhs;
            exp /= 2;
            }
            return *this;
        }
        };
    template< typename T >
    T mod_pow(T x, T n, const T &p) {
        T ret = 1;
        while(n > 0) {
            if(n & 1) (ret *= x) %= p;
            (x *= x) %= p;
            n >>= 1;
        }
        return ret;
    }
    class range {private: struct I{int x;int operator*(){return x;}bool operator!=(I& lhs){return x<lhs.x;}void operator++(){++x;}};I i,n;
    public:range(int n):i({0}),n({n}){}range(int i,int n):i({i}),n({n}){}I& begin(){return i;}I& end(){return n;}};
    uint64_t my_rand(void) {
	static uint64_t x = 88172645463325252ULL;
	x = x ^ (x << 13); x = x ^ (x >> 7);
	return x = x ^ (x << 17);
}
#endif
//library
bool C(vector<ll> &A, ll x, ll K){
    ll res = 0;
    for(auto a:A){
        if(a == 0 ){
            if(x>=0) res+=SZ(A)-1;
            continue;
        }
        ll r = (x%abs(a)+abs(a))%abs(a);
        ll y = (x-r)/a;
        if(a>0){
            ll j = distance(begin(A), upper_bound(all(A), y));
            res+=j;
            if(j>0 && A[j-1]>=a) res-=1;
        }else if (a == 0){
            if(x<=0) res+=SZ(A)-1;
        }else{
            ll j = distance(begin(A), lower_bound(all(A), y));
            res+=(SZ(A)-j);
            if(j!= SZ(A) && A[j]<=a) res-=1;
        }
    }
    if(K<=res/2) return true;
    return false;
}
//main
int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    ll N, K;
    cin >> N >> K;
    vector<ll> A(N);
    rep(i, N)cin >> A[i];
    sort(all(A));
    ll ok = pow(10, 18), ng = -pow(10, 18)-1;
    while(ok-ng>1){
        ll mid = (ok+ng)/2;
        if(C(A, mid, K)) ok = mid;
        else ng = mid;
    }
    C(A, 6, K);
    cout << ok << endl;
}


Measured memory_bytes: 1792