#include <bits/stdc++.h>
#ifdef LOCAL_DEBUG
#define DEBUG 1
#define CERR if(DEBUG) cerr
#define MACRO(_1,_2,_3,_4,_5,_6,_7,_8,_9,_10,NAME,...) NAME
#define pr(...) CERR<<MACRO(__VA_ARGS__,pr10,pr9,pr8,pr7,pr6,pr5,pr4,pr3,pr2,pr1)(__VA_ARGS__)<<endl
#define pr1(a) (#a)<<"="<<(a)<<" "
#define pr2(a,b) pr1(a)<<pr1(b)
#define pr3(a,b,c) pr1(a)<<pr2(b,c)
#define pr4(a,b,c,d) pr1(a)<<pr3(b,c,d)
#define pr5(a,b,c,d,e) pr1(a)<<pr4(b,c,d,e)
#define pr6(a,b,c,d,e,f) pr1(a)<<pr5(b,c,d,e,f)
#define pr7(a,b,c,d,e,f,g) pr1(a)<<pr6(b,c,d,e,f,g)
#define pr8(a,b,c,d,e,f,g,h) pr1(a)<<pr7(b,c,d,e,f,g,h)
#define pr9(a,b,c,d,e,f,g,h,i) pr1(a)<<pr8(b,c,d,e,f,g,h,i)
#define pr10(a,b,c,d,e,f,g,h,i,j) pr1(a)<<pr9(b,c,d,e,f,g,h,i,j)
#define prArr(a){CERR<<(#a)<<"={";int i=0;for(auto t:(a))CERR<<(i++?", ":"")<<t;CERR<<"}"<<endl;}
#else
#define DEBUG 0
#define pr(...)
#define prArr(a)
#endif
using namespace std;
using Int = long long;
using _int = int;
using ll = long long;
using Double = long double;
const Int INF = (1LL<<60)+1e9; // ~ 1.15 * 1e18
const Int mod = (1e9)+7;
const Double EPS = 1e-8;
const Double PI = 6.0 * asin((Double)0.5);
using P = pair<Int,Int>;
template<class T> T Max(T &a,T b){return a=max(a,b);}
template<class T> T Min(T &a,T b){return a=min(a,b);}
template<class T1, class T2> ostream& operator<<(ostream& o,pair<T1,T2> p){return o<<"("<<p.first<<","<<p.second<<")";}
template<class T1, class T2, class T3> ostream& operator<<(ostream& o,tuple<T1,T2,T3> t){return o<<"("<<get<0>(t)<<","<<get<1>(t)<<","<<get<2>(t)<<")";}
template<class T1, class T2> istream& operator>>(istream& i,pair<T1,T2> &p){return i>>p.first>>p.second;}
template<class T> ostream& operator<<(ostream& o,vector<T> a){Int i=0;for(T t:a)o<<(i++?" ":"")<<t;return o;}
template<class T> istream& operator>>(istream& i,vector<T> &a){for(T &t:a)i>>t;return i;}
//INSERT ABOVE HERE


signed main(){
  srand((unsigned)time(NULL));
  cin.tie(0);
  ios_base::sync_with_stdio(0);
  cout << fixed << setprecision(12);

  Int N, K;
  cin>>N>>K;
  vector<Int> A(N);
  cin>>A;
  sort(A.begin(), A.end());
  vector<Int> pA, nA;
  for(Int a:A){
    if(a >= 0) pA.push_back(a);
    else nA.push_back(a);
  }
  reverse(nA.begin(), nA.end());

  auto check = [&](Int x){

    auto count=[&](Int a){
      //count a * v <= x;
      Int s, t = 0;
      {
        Int L = -1, R = pA.size();
        while(L + 1 < R){
          Int M = (L + R) / 2;
          Int f = 0;
          if(a * pA[M] <= x) f = a >= 0;
          else f = a < 0;
          f? (L = M):(R = M);
        }
        s = a >= 0? R:(Int)pA.size() - R;
      }
      {
        Int L = -1, R = nA.size();
        while(L + 1 < R){
          Int M = (L + R) / 2;
          Int f = 0;
          if(a * nA[M] <= x) f = a <= 0;
          else f = a > 0;
          f? (L = M):(R = M);
        }
        t = a <= 0? R:(Int)nA.size() - R;
      }
      Int res = s + t;
      pr(a, s, t, res);
      return res;
    };

    Int num = 0;
    for(Int a:A){
      num += count(a);
      if(a * a <= x) num--;
    }
    assert(num % 2 == 0);
    num /= 2;
    pr(x, K, num);
    return num < K;
  };

  if(0){
    Int f = check(6);
    pr(f);
    return 0;
  }
  Int L = -(1e18) + 100, R = (1e18) + 100;
  while(L + 1 < R){
    Int M = (L + R) / 2;
    check(M)? (L = M):(R = M);
  }

  Int ans = R;
  cout<<ans<<endl;


  return 0;
}


Measured memory_bytes: 4084