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

#define REP(i,n) for(ll i=0;i<(ll)n;i++)
#define dump(x)  cerr << #x << " = " << (x) << endl;
#define spa << " " <<
#define fi first
#define se second
#define ALL(a)  (a).begin(),(a).end()
#define ALLR(a)  (a).rbegin(),(a).rend()

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

template<typename T> struct V : vector<T> { using vector<T>::vector; };
V() -> V<ll>;
V(size_t) -> V<ll>;
template<typename T> V(size_t, T) -> V<T>;
template<typename T> vector<T> make_vec(size_t n, T a) { return vector<T>(n, a); }
template<typename... Ts> auto make_vec(size_t n, Ts... ts) { return vector<decltype(make_vec(ts...))>(n, make_vec(ts...)); }
template<class S, class T> ostream& operator << (ostream& os, const pair<S, T> v){os << "(" << v.first << ", " << v.second << ")"; return os;}
template<typename T> ostream& operator<<(ostream &os, const vector<T> &v) { for (auto &e : v) os << e << ' '; return os; }
template<class T> ostream& operator<<(ostream& os, const vector<vector<T>> &v){ for(auto &e : v){os << e << "\n";} return os;}
struct fast_ios { fast_ios(){ cin.tie(nullptr); ios::sync_with_stdio(false); cout << fixed << setprecision(20); }; } fast_ios_;

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 (a>b) { a=b; return 1; } return 0; }
void fail() { cout << -1 << '\n'; exit(0); }
inline int popcount(const int x) { return __builtin_popcount(x); }
inline int popcount(const ll x) { return __builtin_popcountll(x); }
template<typename T> void debug(vector<vector<T>>&v,ll h,ll w){for(ll i=0;i<h;i++)
{cerr<<v[i][0];for(ll j=1;j<w;j++)cerr spa v[i][j];cerr<<endl;}};
template<typename T> void debug(vector<T>&v,ll n){if(n!=0)cerr<<v[0];
for(ll i=1;i<n;i++)cerr spa v[i];
cerr<<endl;};

const ll INF = (1ll<<62);
// const ld EPS   = 1e-10;
// const ld PI    = acos(-1.0);
const ll mod = (int)1e9 + 7;
//const ll mod = 998244353;

int main(){

    ll N, K;
    cin >> N >> K;
    V<ll> A(N);
    REP(i, N) cin >> A[i];

    ll MA = 1e18;
    ll ng = -MA-1;
    ll ok = MA+1;

    V<ll> pos, neg;
    ll z = 0;
    for(auto a: A){
        if(a>0) pos.push_back(a);
        else if(a<0) neg.push_back(-a);
        else z++;
    }

    sort(ALL(pos));
    sort(ALL(neg));

    // dump(pos)
    // dump(neg)

    ll ps = pos.size();
    ll ns = neg.size();

    auto judge = [&](ll x){
        ll res = 0;
        if(x>=0){
            res += ps * ns;
            res += z * (ps + ns);
            res += z*(z-1)/2;

            REP(i, ps){
                ll tmp = upper_bound(pos.begin()+i+1, pos.end(), x/pos[i]) - (pos.begin()+i+1);
                res += tmp;
            }

            REP(i, ns){
                ll tmp = upper_bound(neg.begin()+i+1, neg.end(), x/neg[i]) - (neg.begin()+i+1);
                res += tmp;
            }
        }else{
            REP(i, ps){
                ll tmp = neg.end() - lower_bound(neg.begin(), neg.end(), (-x+pos[i]-1)/pos[i]);
                res += tmp;
            }
        }
        return res;
    };

    while(ok-ng>1){
        ll md = (ok+ng)/2;
        if(judge(md)>=K) ok = md;
        else ng = md;
    }

    cout << ok << endl;

    return 0;
}

Measured memory_bytes: 6668