///////////////////////////////////////////////////////////////////////////////

#include <bits/stdc++.h>
#include <unistd.h>
#include <time.h>
#include <sys/time.h>

using namespace std;

///////////////////////////////////////////////////////////////////////////////

#define DEBUG 0

#define pb push_back
#define V vector
#define M unordered_map
#define S static

#define rep(i,n) for(ll i=0LL; i<n; ++i)
#define srep(i,s,n) for(ll i=s; i<n; ++i)
#define rrep(i,n) for(ll i=n-1LL; i>=0LL; --i)
#define ALL(a) (a).begin(),(a).end()
#define RALL(a) (a).rbegin(),(a).rend()
#define CIN(x) do { \
        assert(!cin.eof()); \
        cin >> x; \
        assert(!cin.fail()); \
} while(0);
#if DEBUG
#define debug_print(...) _debug_print(__VA_ARGS__)
#define debug_printf(...) printf(__VA_ARGS__)
#define debug_print_time _debug_print_time
#else // DEBUG
#define debug_print(...)
#define debug_printf(...)
#define debug_print_time
#endif // DEBUG

typedef long long ll;
typedef unsigned long long ull;
typedef tuple<ll, ll> t2;
typedef tuple<ll, ll, ll> t3;
typedef tuple<ll, ll, ll, ll> t4;
typedef tuple<ll, ll, ll, ll, ll> t5;
template <typename T>
using priority_queue_incr = priority_queue<T, V<T>, greater<T> >;

///////////////////////////////////////////////////////////////////////////////

template <typename TT, typename T>
T get_m(M<TT, T> &m, TT k, T default_value)
{
    if (m.find(k) == m.end()) return m[k] = default_value;
    return m[k];
}

template <typename TT, typename T>
void incr_m(M<TT, T> &m, TT k)
{
    if (m.find(k) == m.end()) m[k] = 0;
    m[k]++;
}

template <typename TT, typename T>
void incr_m(map<TT, T> &m, TT k)
{
    if (m.find(k) == m.end()) m[k] = 0;
    m[k]++;
}

void llin(ll &a)
{
    CIN(a);
}

void llinl1(V<ll> &v, ll count)
{
    for (ll i = 0LL; i < count; ++i) {
        ll a;
        CIN(a);
        v.push_back(a);
    }
}

void llinl2(V<t2> &v, ll count)
{
    for (ll i = 0LL; i < count; ++i) {
        ll a, b;
        CIN(a >> b);
        v.push_back(t2(a, b));
    }
}

void llinl3(V<t3> &v, ll count)
{
    for (ll i = 0LL; i < count; ++i) {
        ll a, b, c;
        CIN(a >> b >> c);
        v.push_back(t3(a, b, c));
    }
}

void llinl4(V<t4> &v, ll count)
{
    for (ll i = 0LL; i < count; ++i) {
        ll a, b, c, d;
        CIN(a >> b >> c >> d);
        v.push_back(t4(a, b, c, d));
    }
}

void llina(V<ll> &v, ll count)
{
    llinl1(v, count);
}

template <typename T>
void sort(V<T> &v)
{
    sort(v.begin(), v.end());
}

template <typename T>
void sort_reverse(V<T> &v)
{
    sort(v.begin(), v.end(), greater<T>());
}

template <typename T>
void _debug_print(T x)
{
    cout << x << endl;
}

void _debug_print(const t2 &x)
{
    ll x1 = get<0>(x);
    ll x2 = get<1>(x);
    cout << "-- " << x1 << " -- " << x2 << endl;
}

void _debug_print(const t3 &x)
{
    ll x1 = get<0>(x);
    ll x2 = get<1>(x);
    ll x3 = get<2>(x);
    cout << "-- " << x1 << " -- " << x2 << " -- " << x3 << endl;
}

void _debug_print(const t4 &x)
{
    ll x1 = get<0>(x);
    ll x2 = get<1>(x);
    ll x3 = get<2>(x);
    ll x4 = get<3>(x);
    cout << "-- " << x1 << " -- " << x2
         << " -- " << x3 << " -- " << x4 << endl;
}

template <typename T>
void _debug_print(T xarray[], ll n)
{
    rep (i, n) _debug_print(xarray[i]);
}

template <typename T>
void _debug_print(const V<T> &xlist)
{
    for (auto x : xlist) {
        cout << "-- ";
        _debug_print(x);
    }
}

template <typename T>
void _debug_print(const set<T> &xset)
{
    for (auto x : xset) {
        cout << "-- ";
        _debug_print(x);
    }
}

template <typename TT, typename T>
void _debug_print(const M<TT, T> &xlist)
{
    for (auto x : xlist) {
        TT k = x.first;
        T v = x.second;
        cout << "====" << endl;
        cout << "K=";
        _debug_print(k);
        cout << "V=";
        _debug_print(v);
    }
}

template <typename TT, typename T>
void _debug_print(const map<TT, T> &xlist)
{
    for (auto x : xlist) {
        TT k = x.first;
        T v = x.second;
        cout << "====" << endl;
        cout << "K=";
        _debug_print(k);
        cout << "V=";
        _debug_print(v);
    }
}

void _debug_print_time(const char *prefix)
{
    struct timeval tv;
    gettimeofday(&tv, NULL);
#if DEBUG
    struct tm *tm = localtime(&tv.tv_sec);
#endif
    debug_printf("-- %s %02d:%02d:%02d.%06ld\n",
                  prefix, tm->tm_hour, tm->tm_min, tm->tm_sec, tv.tv_usec);
}

///////////////////////////////////////////////////////////////////////////////

void _main();
int main()
{
    cout << setprecision(12);
#if !DEBUG
    ios::sync_with_stdio(false);
    cin.tie(0);
#endif

    _main();
    return 0;
}

void solve_neg(V<ll> &negs, V<ll> &poss, ll k)
{
    sort(negs);

    ll floor = 1;
    ll ceil = 1e18;
    ll now_ngval = (floor+ceil)/2LL;
    ll ans = 1e18;

    for ( ; floor <= ceil; now_ngval = (floor+ceil)/2LL) {
        ll cnt = 0;
        for (auto a : poss) {
            ll ng = now_ngval / a;
            auto end = lower_bound(ALL(negs), -ng);
            cnt += (end - negs.begin());
        }
        if (cnt <= k) {
            ans = min(ans, now_ngval);
            ceil = now_ngval - 1LL;
        }
        else {
            floor = now_ngval + 1LL;
        }
    }

    ans = -ans;

    debug_printf("---- solve_neg ans\n");
    cout << ans << endl;
}

void solve_pos(V<ll> &negs, V<ll> &poss, ll k)
{
    V<ll> g[2];
    for (auto a : negs) g[0].pb(abs(a));
    g[1] = poss;
    rep (i, 2) sort(g[i]);

    debug_printf("k=%lld\n", k);
    rep (i, 2) {
        debug_printf("---- g[%lld]\n", i);
        debug_print(g[i]);
    }

    ll left = 1;
    ll right = 1e18;
    ll now_ngval = (left+right)/2LL;
    ll ans = 1;

    for ( ; left <= right; now_ngval = (left+right)/2LL) {
        ll cnt = 0;
        rep (i, 2) {
            rep (j, g[i].size()) {
                ll ng = now_ngval / g[i][j] + !!(now_ngval % g[i][j]);
                auto start = g[i].begin() + j + 1;
                auto end = lower_bound(start, g[i].end(), ng);
                cnt += (end - start);
            }
        }
        if (now_ngval < 10) debug_printf("now_ngval=%lld cnt=%lld\n", now_ngval, cnt);
        if (cnt <= k) {
            ans = max(ans, now_ngval);
            left = now_ngval + 1LL;
        }
        else {
            right = now_ngval - 1LL;
        }
    }

    debug_printf("---- ans solve_pos\n");
    cout << ans << endl;
}

void _main()
{
    ll n; llin(n);
    ll k; llin(k);
    S V<ll> alist; llina(alist, n);

    k--;

    S V<ll> negs, poss;
    ll zerocnt = 0;
    for (auto a : alist) {
        if (a < 0) negs.pb(a);
        if (a > 0) poss.pb(a);
        if (a == 0) zerocnt++;
    }

    ll res_negcnt = negs.size() * poss.size();
    ll res_zerocnt = zerocnt * (negs.size() + poss.size());
    res_zerocnt += zerocnt * (zerocnt-1LL) / 2LL;

    if (k < res_negcnt) {
        solve_neg(negs, poss, k);
        return;
    }
    k -= res_negcnt;

    if (k < res_zerocnt) {
        cout << 0 << endl;
        return;
    }
    k -= res_zerocnt;

    solve_pos(negs, poss, k);
}

///////////////////////////////////////////////////////////////////////////////


Measured memory_bytes: 9096