#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ld = long double;
using VI = vector<int>;
using VL = vector<ll>;
template<class T> using PQ = priority_queue<T, vector<T>, greater<T>>;
#define FOR(i,a,n) for(ll (i)=(a);(i)<(n);++(i))
#define eFOR(i,a,n) for(int (i)=(a);(i)<=(n);++(i))
#define rFOR(i,a,n) for(int (i)=(n)-1;(i)>=(a);--(i))
#define erFOR(i,a,n) for(int (i)=(n);(i)>=(a);--(i))
#define each(i, a) for(auto &i : a)
#define SORT(i) sort((i).begin(),(i).end())
#define rSORT(i,a) sort((i).begin(),(i).end(),(a))
#define all(i) (i).begin(),(i).end()
#define out(y,x) ((y) < 0 || h <= (y) || (x) < 0 || w <= (x))
#define line cout << "------------------------\n" 
#define ENDL(i,n) ((i) == (n) - 1 ? "\n" : " ")
#define stop system("pause") //comment out this on AOJ.
constexpr ll INF = 1000000000;
constexpr ll LLINF = 1LL << 60;
constexpr ll mod = 1000000007;
constexpr ll MOD = 998244353;
constexpr ld eps = 1e-10; //1e-9?
constexpr ld pi = 3.1415926535897932;
template<class T>inline bool chmax(T& a, T b) { if (a < b) { a = b; return true; }return false; }
template<class T>inline bool chmin(T& a, T b) { if (a > b) { a = b; return true; }return false; }
inline void init() { cin.tie(nullptr); cout.tie(nullptr); ios::sync_with_stdio(false); cout << fixed << setprecision(15); }
template<class T>inline istream& operator>>(istream& is, vector<T>& v) { for (auto& elemnt : v)is >> elemnt; return is; }
template<class T, class U>inline istream& operator>>(istream& is, pair<T, U>& p) { is >> p.first >> p.second; return is; }
template<class T>inline vector<T> vec(size_t a) { return vector<T>(a); }
template<class T>inline vector<T> defvec(T def, size_t a) { return vector<T>(a, def); }
template<class T, class... Ts>inline auto vec(size_t a, Ts... ts) { return vector<decltype(vec<T>(ts...))>(a, vec<T>(ts...)); }
template<class T, class... Ts>inline auto defvec(T def, size_t a, Ts... ts) { return vector<decltype(defvec<T>(def, ts...))>(a, defvec<T>(def, ts...)); }

int main() {
    init();

    ll n, k; cin >> n >> k;
    VL pos, neg;
    ll zero = 0;
    FOR(i, 0, n) {
        ll in; cin >> in;
        if (0 < in)pos.push_back(in);
        else if (in < 0)neg.push_back(in);
        else ++zero;
    }
    ll a = pos.size(), b = neg.size();

    ll s1 = a * b, s2 = zero * (a + b) + zero * (zero - 1) / 2,
        s3 = a * (a - 1) / 2 + b * (b - 1) / 2;

    if (k <= s1) {
        rSORT(pos, greater<ll>());
        SORT(neg);
        ll ok = -1, ng = -1e18;
        while (ok - ng > 1) {
            ll x = (ok + ng) / 2;
            bool check;
            {
                ll cnt = 0;
                FOR(i, 0, a) {
                    ll ok = -1, ng = b;
                    while (ng - ok > 1) {
                        ll mid = (ok + ng) / 2;
                        if (pos[i] * neg[mid] <= x)ok = mid;
                        else ng = mid;
                    }
                    cnt += ok + 1;
                }
                FOR(i, 0, b) {
                    ll ok = -1, ng = a;
                    while (ng - ok > 1) {
                        ll mid = (ok + ng) / 2;
                        if (neg[i] * pos[mid] <= x)ok = mid;
                        else ng = mid;
                    }
                    cnt += ok + 1;
                }
                check = k <= cnt / 2;
            }
            if (check)ok = x;
            else ng = x;
        }
        cout << ok << "\n";
    }
    else if (k <= s1 + s2)cout << "0\n";
    else {
        SORT(pos);
        rSORT(neg, greater<ll>());
        k -= s1 + s2;
        ll ok = 1e18, ng = 0;
        while (ok - ng > 1) {
            ll x = (ok + ng) / 2;
            bool check;
            {
                ll cnt = 0;
                FOR(i, 0, a) {
                    ll ok = i, ng = a;
                    while (ng - ok > 1) {
                        ll mid = (ok + ng) / 2;
                        if (pos[i] * pos[mid] <= x)ok = mid;
                        else ng = mid;
                    }
                    cnt += ok - i;
                }
                FOR(i, 0, b) {
                    ll ok = i, ng = b;
                    while (ng - ok > 1) {
                        ll mid = (ok + ng) / 2;
                        if (neg[i] * neg[mid] <= x)ok = mid;
                        else ng = mid;
                    }
                    cnt += ok - i;
                }
                check = k <= cnt;
            }
            if (check)ok = x;
            else ng = x;
        }
        cout << ok << "\n";
    }
}

Measured memory_bytes: 2420