#include <bits/stdc++.h>
#include <ext/rope>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
//#pragma GCC optimize("Ofast")
//#pragma GCC optimize("unroll-loops")
//#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
//#define int long long
#define pb push_back
#define x first
#define y second
#define mk(a,b) make_pair(a,b)
#define rr return 0
#define sqr(a) ((a)*(a))
#define all(a) (a).begin(), (a).end()
#define sz(a) (int)(a).size()

using namespace std;
using namespace __gnu_cxx;
using namespace __gnu_pbds;

using ll = long long;
using ld = long double;
using pii = pair<int, int>;
using pll = pair<ll, ll>;

template<class value, class cmp = less<value> >
using ordered_set = tree<value, null_type, cmp, rb_tree_tag, tree_order_statistics_node_update>;
template<class value, class cmp = less_equal<value> >
using ordered_multiset = tree<value, null_type, cmp, rb_tree_tag, tree_order_statistics_node_update>;
template<class key, class value, class cmp = less<key> >
using ordered_map = tree<key, value, cmp, rb_tree_tag, tree_order_statistics_node_update>;

/// find_by_order()
/// order_of_key()
mt19937 rng(chrono::high_resolution_clock::now().time_since_epoch().count());
inline int randll(int l = INT_MIN, int r = INT_MAX) {
    return uniform_int_distribution<int>(l, r)(rng);
}
const int INF = 1e9, MOD = 1e9 + 7; /// think
const ll LINF = 1e18;


const int dx[] = {0, 0, 1, -1}, dy[] = {1, -1, 0, 0};
inline bool inside (int x, int y, int n, int m) {
    return 0 <= x && 0 <= y && x < n && y < m;
}

template<class T> bool umin (T &a, T b) {return a > b ? (a = b, true) : false; }
template<class T> bool umax (T &a, T b) {return a < b ? (a = b, true) : false; }

main()
{
    ios::sync_with_stdio(0);
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    int n;
    ll k;
    cin >> n >> k;
    vector <int> pos, neg;
    int zero = 0;
    for (int i = 0, x; i < n; i++) {
        cin >> x;
        if (x == 0) {
            ++zero;
            continue;
        }
        if (x > 0) {
            pos.pb(x);
        }
        else neg.pb(x);
    }
    sort(all(pos));
    sort(all(neg));
    ll l = -LINF - 11, r = LINF + 11;
    auto f = [&] (ll mid) {
        ll cnt = 0;
        for (int i = sz(pos) - 1, j = 0; i >= 0; i--){
            while (j < sz(pos) && ((ll)pos[i] * pos[j]) < mid) {
                ++j;
            }
            cnt += j;
        }
        for (int i = 0, j = sz(neg) - 1; i < sz(neg); i++) {
            while (j >= 0 && ((ll)neg[i] * neg[j]) < mid) {
                --j;
            }
            cnt += sz(neg) - 1 - j;
        }
        for (auto &i : pos) {
            if ((ll)i * i < mid) --cnt;
        }
        for (auto &i : neg) {
            if ((ll)i * i < mid) --cnt;
        }
        assert(cnt % 2 == 0);
        cnt /= 2;
        if (mid > 0) {
            cnt += zero * 1ll * (n - zero) + zero * (zero - 1ll) / 2ll;
        }
        for (int i = sz(neg) - 1, j = sz(pos) - 1; i >= 0; i--) {
            while (j >= 0 && (ll)neg[i] * pos[j] < mid) {
                --j;
            }
            cnt += sz(pos) - 1 - j;
        }
        return cnt;
    };
    while (l < r) {
        ll mid = (l + r + 1ll) >> 1ll;
        if (f(mid) < k) l = mid;
        else r = mid - 1;
    }
    cout << r << '\n';
//    cout << f(r) << '\n';
//    cout << f(448283280358331064ll) << '\n';
}


Measured memory_bytes: 4348