/*

  "With age, comes wisdom. With travel, comes understanding.
   Remember that happiness is a way of travel – not a destination"

*/

#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>

using namespace std;
using namespace __gnu_pbds;

#define int            long long int
#define F              first
#define S              second
#define pb             push_back
#define si             set <int>
#define vi             vector <int>
#define pii            pair <int, int>
#define vpi            vector <pii>
#define vpp            vector <pair<int, pii>>
#define mii            map <int, int>
#define mpi            map <pii, int>
#define spi            set <pii>
#define endl           "\n"
#define sz(x)          ((int) x.size())
#define all(p)         p.begin(), p.end()
#define double         long double
#define que_max        priority_queue <int>
#define que_min        priority_queue <int, vi, greater<int>>
#define bug(...)       __f (#__VA_ARGS__, __VA_ARGS__)
#define print(a)       for(auto x : a) cout << x << " "; cout << endl
#define print1(a)      for(auto x : a) cout << x.F << " " << x.S << endl
#define print2(a,x,y)  for(int i = x; i < y; i++) cout<< a[i]<< " "; cout << endl

inline int power(int a, int b)
{
     int x = 1;
     while (b)
     {
          if (b & 1) x *= a;
          a *= a;
          b >>= 1;
     }
     return x;
}

typedef tree<pii, null_type, less<pii>, rb_tree_tag, tree_order_statistics_node_update> Set;

template <typename Arg1>
void __f (const char* name, Arg1&& arg1) { cout << name << " : " << arg1 << endl; }
template <typename Arg1, typename... Args>
void __f (const char* names, Arg1&& arg1, Args&&... args)
{
     const char* comma = strchr (names + 1, ',');
     cout.write (names, comma - names) << " : " << arg1 << " | "; __f (comma + 1, args...);
}

const int N = 200005;
int n, m, k;
vi a, b, c;


bool check(int mx)
{
     int cnt = 0, cnt1 = 0;
     for (auto x : a)
     {
          int l = 0, h = sz(a) - 1, ans = 0;
          while (l <= h)
          {
               int mid = l + h >> 1;
               if (a[mid]*x < mx)
                    l = mid + 1, ans = mid + 1;
               else
                    h = mid - 1;
          }
          if (x * x < mx)
               ans--;

          cnt += ans;
     }
     for (auto x : a)
     {
          int l = 0, h = sz(b) - 1, ans = 0;
          while (l <= h)
          {
               int mid = l + h >> 1;
               if (b[mid]*x < mx)
                    h = mid - 1, ans = sz(b) - mid;
               else
                    l = mid + 1;
          }
          cnt1 += ans;
     }
     for (auto x : b)
     {
          int l = 0, h = sz(b) - 1, ans = 0;
          while (l <= h)
          {
               int mid = l + h >> 1;
               if (b[mid]*x < mx)
                    l = mid + 1, ans = mid + 1;
               else
                    h = mid - 1;
          }
          if (x * x < mx)
               ans--;

          cnt += ans;
     }

     cnt /= 2; cnt += cnt1;
     if (mx > 0)
          cnt += (n - sz(c)) * sz(c) + (sz(c) * (sz(c) - 1)) / 2;

     return cnt < k;

}

void solve()
{
     cin >> n >> k;
     for (int i = 0; i < n; i++)
     {
          int x; cin >> x;
          if (x < 0)
               b.pb(x);
          else if (x > 0)
               a.pb(x);
          else
               c.pb(x);
     }

     sort(all(a));
     sort(b.rbegin(), b.rend());

     int l = -1e18, h = 1e18, ans = 0;
     while (l <= h)
     {
          int mid = l + h >> 1;
          if (check(mid))
               l = mid + 1, ans = mid;
          else
               h = mid - 1;
     }

     cout << ans;


}

int32_t main()
{
     ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);

     cout << setprecision(9) << fixed;
     clock_t z = clock();
     solve();
     cerr << "Run Time : " << ((double)(clock() - z) / CLOCKS_PER_SEC);

     return 0;
}

Measured memory_bytes: 2548