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

typedef long long ll;
typedef vector<ll> vll;
typedef vector<vector<ll>> vvll;
typedef vector<vector<vector<ll>>> vvvll;
typedef vector<bool> vb;
typedef vector<vector<bool>> vvb;
typedef vector<vector<vector<bool>>> vvvb;
typedef pair<ll, ll> pll;
typedef vector<pll> vpll;
typedef vector<vpll> vvpll;
typedef vector<double> vd;
typedef vector<vd> vdd;

#define FOR(i,x,y) for(ll i=(ll)x; i<(ll)y; ++i)
#define REP(i,y) FOR(i, 0, y)
#define RFOR(i,x,y) for(ll i=(ll)x; i>=(ll)y; --i)
#define RREP(i,x) RFOR(i, x, 0)
#define ALL(a) a.begin(), a.end()
#define pb push_back
#define debug_print(x...) cerr << "line " << __LINE__ << " : "; debug_print_in(x);

template <typename First>
void debug_print_in(First first){
  cerr << first << endl;
  return;
}

template <typename First, typename... Rest>
void debug_print_in(First first, Rest... rest){
  cerr << first << " ";
  debug_print_in(rest...);
  return;
}

void IN(void){
  return;
}

template <typename First, typename... Rest>
void IN(First& first, Rest&... rest){
  cin >> first;
  IN(rest...);
  return;
}

template <typename First>
void OUT(First first){
  cout << first << endl;
  return;
}

template <typename First, typename... Rest>
void OUT(First first, Rest... rest){
  cout << first << " ";
  OUT(rest...);
  return;
}

template<class t, class u> void chmax(t&a,u b){if(a<b)a=b;};
template<class t, class u> void chmin(t&a,u b){if(a>b)a=b;};
int popcount(int t){return __builtin_popcount(t);} //GCC
int popcount(ll t){return __builtin_popcountll(t);} //GCC

template <typename T>
void vec_print(vector<T> VEC){
  REP(i, VEC.size()){
    cerr << VEC[i] << " ";
  }
  cerr << endl;
};

template <typename T>
void mat_print(vector<vector<T> > MAT){
  REP(i,MAT.size()){
    REP(j,MAT[i].size()){
      cerr << MAT[i][j] << " ";
    }
    cerr << endl;
  }
};

constexpr int INF = (1<<30);
constexpr ll INFLL = 1LL<<62;
constexpr long double EPS = 1e-12;
constexpr ll MOD = (ll)((1E+9)+7);

ll N, K;
vll A;

ll Bp(ll low, ll high, ll tmp, ll val){
  if(high-low<=1){
    if(tmp*A[high]<=val) return high;
    return low;
  }
  ll mid = (high+low)/2;
  if(tmp*A[mid]<=val) return Bp(mid, high, tmp, val);
  return Bp(low, mid, tmp, val);
}

ll Bm(ll low, ll high, ll tmp, ll val){
  if(high-low<=1){
    if(tmp*A[high]>val) return high;
    return low;
  }
  ll mid = (high+low)/2;
  if(tmp*A[mid]>val) return Bm(mid, high, tmp, val);
  return Bm(low, mid, tmp, val);
}

ll count(ll val){
  ll ans = 0;
  REP(i,N){
    ll tmp = A[i];
    ll tmp3 = 0;
    if(tmp==0){
      if(val>=0) tmp3 = N;
    }else if(tmp>0){
      /*
      ll tmp2 = val/tmp;
      while(tmp2*tmp<=val) tmp2++;
      while(tmp2*tmp>val) tmp2--;
      tmp3 = upper_bound(ALL(A), tmp2) - A.begin() - 1;
      */
      tmp3 = Bp(-1, N-1, tmp, val);
      //if(tmp3*A[0]>val) tmp3--;
      tmp3++;
      //debug_print(val, tmp, tmp3);
    }else{
      /*
      ll tmp2 = val/tmp;
      while(tmp2*tmp<=val) tmp2--;
      while(tmp2*tmp>val) tmp2++;
      tmp3 = N-(lower_bound(ALL(A), tmp2) - A.begin());
      */
      tmp3 = Bm(-1, N-1, tmp, val);
      //debug_print(val, tmp, tmp3);
      //if(tmp3*A[0]<=val) tmp3--;
      tmp3 = N-(tmp3+1);
    }
    ans += tmp3;
    if(A[i]*A[i]<=val) ans--;
  }
  /*
  REP(i,N){
    REP(j,N){
      if(A[i]*A[j]<=val) ans++;
    }
    if(A[i]*A[i]<=val) ans--;
  }
  */
  return ans/2;
}

ll binary_search(ll low, ll high){
  if(high-low<=1){
    if(count(low)==K) return low;
    return high;
  }
  ll mid = (low+high)/2;
  if(count(mid)>=K) return binary_search(low, mid);
  return binary_search(mid, high);
}

int main(){
  cin.tie(0); // cut the cin and cout (default, std::flush is performed after std::cin)
  ios::sync_with_stdio(false); // cut the iostream and stdio (DON'T endl; BUT "\n";)

  IN(N, K);
  A.resize(N);
  REP(i,N) IN(A[i]);
  sort(ALL(A));

  OUT(binary_search(-1E18, 1E18));

  return 0;
}

Measured memory_bytes: 1792