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

// clang-format off
#define  range(i, l, r) for (int i = (int)(l); i < (int)(r); ++(i))
#define rrange(i, l, r) for (int i = (int)(r) - 1; i >= (int)(l); --(i))

#define  whole(f, x, ...) ([&](decltype((x)) container) { return (f)(  begin(container),  end(container), ## __VA_ARGS__); })(x)
#define rwhole(f, x, ...) ([&](decltype((x)) container) { return (f)( rbegin(container), rend(container), ## __VA_ARGS__); })(x)

#define endl '\n'
#define debug(x) cerr << "(" << __LINE__ << ")" << #x << ": " << (x) << endl

using i32 = int;
using u32 = unsigned int;
using i64 = long long;
using u64 = unsigned long long;

constexpr i32 mod   = 1e9 + 7;
constexpr i32 inf   = 1001001001;
constexpr i64 infll = 1001001001001001001ll;

constexpr int dx[] = {0, -1, 1, 0, -1, 1, -1, 1}; 
constexpr int dy[] = {-1, 0, 0, 1, -1, -1, 1, 1};

struct IoSetup { IoSetup(int x = 15){ cin.tie(0); ios::sync_with_stdio(0); cout << fixed << setprecision(x); cerr << fixed << setprecision(x); } } iosetup;

template <typename T = i64> T input() { T x; cin >> x; return x; }

template <typename T> ostream &operator<<(ostream &os, vector<T> &v) { range(i, 0, v.size()) { os << v[i] << (i + 1 != v.size() ? " " : ""); } return os; } 
template <typename T> istream &operator>>(istream &is, vector<T> &v) { for (T &in : v) is >> in; return is; }

template <typename T1, typename T2> ostream &operator<<(ostream &os, pair<T1, T2> p) { os << "(" << p.first << ", " << p.second << ")"; return os; }
template <typename T1, typename T2> istream &operator>>(istream &is, pair<T1, T2> &p) { is >> p.first >> p.second; return is; }

template <typename T> vector<T> make_vector(size_t a, T b) { return vector<T>(a, b); }
template <typename... Ts> auto make_vector(size_t a, Ts... ts) { return vector<decltype(make_v(ts...))>(a, make_v(ts...)); }

template <typename T1, typename T2> inline bool chmax(T1 &a, T2 b) { return a < b && (a = b, true); }
template <typename T1, typename T2> inline bool chmin(T1 &a, T2 b) { return a > b && (a = b, true); }
// clang-format on

void solver() {
    i64 N = input(), K = input();
    vector< i64 > a(N);
    cin >> a;

//    {
//        vector< i64 > d;
//        range(i, 0, N) range(j, 0, i) d.push_back(a[i] * a[j]);
//        whole(sort, d);
//        debug(d);
//    }

    whole(sort, a);
    
    vector< i64 > m, z, p;
    for (auto &i: a) {
        if (i < 0) m.push_back(i);
        if (i > 0) p.push_back(i);
        if (i == 0) z.push_back(i);
    }
    
    if (K <= (i64)m.size() * p.size()) {
        i64 ok = -1, ng = -infll; // (ng, ok]
        while (ok - ng > 1) {
            i64 mid = (ok + ng) / 2;
//            cerr << make_pair(ng, ok) << endl;
//            debug(mid);

            int idx = 0;
            i64 cnt = 0;
            range(i, 0, m.size()) {
                while (idx < p.size() && p[idx] * m[i] > mid) idx++;
                cnt += p.size() - idx;
//                if (idx < p.size()) cerr << m[i] << " * " << p[idx] << endl;
            }
//            debug(cnt);
            
            if (cnt < K) ng = mid;
            else ok = mid;
        }
        
        cout << ok << endl;
            
        return;
    }
    
    K -= (i64)m.size() * p.size();
//    debug(K);
    
    if (K <= N * (N - 1) / 2 - (N - z.size()) * (N - z.size() - 1) / 2) {
        cout << 0 << endl;
        return;
    }
    
    K -= N * (N - 1) / 2 - (N - z.size()) * (N - z.size() - 1) / 2;
    
//    debug(K);
//    cerr << "jissousiteimasenn" << endl;
//    swap(m, p);
//    whole(reverse, p);
//    whole(reverse, m);
    {
        i64 ok = infll, ng = 0; // (ng, ok]
        while (ok - ng > 1) {
            i64 mid = (ok + ng) / 2;
//            cerr << make_pair(ng, ok) << endl;
//            debug(mid);

            i64 cnt = 0;
            i32 idx = p.size() - 1;
//            debug(p);
            range(i, 0, p.size()) {
                while (idx >= 0 && p[i] * p[idx] > mid) idx--;
//                i64 add = idx + 1;
//                if (idx >= i) add--;
                i64 add = max(0, idx - i);
                cnt += add;
//                if (idx >= 0) cerr << p[i] << " * " << p[idx] << endl;
            }
//            debug(cnt);
            
            idx = 0;
//            debug(m);
            rrange(i, 0, m.size()) {
                while (idx < m.size() && m[i] * m[idx] > mid) idx++;
//                i64 add = m.size() - idx;
//                if (idx <= i) add--;
                i64 add = max(0, i - idx);
                cnt += add;
//                if (idx < m.size()) cerr << m[i] << " * " << m[idx] << endl;
            }

//            debug(cnt);
            
            if (cnt < K) ng = mid;
            else ok = mid;
        }
        
        cout << ok << endl;
    }
}

signed main(int argc, char *argv[]) {
    solver();
}


Measured memory_bytes: 4468