#include <iostream>
#include <algorithm>
using namespace std;
typedef long long ll;

int binary_search(int n,ll *a,int i,ll trg){
  int l,r,mid;
  l=-1;
  r=n;
  
  if (a[i]>=0){
    while (r-l>1){
      mid=(l+r)/2;
      if (a[i]*a[mid] <= trg) l=mid;
      else r=mid;
    }
    if (l>=i) return l;
    else return l+1;
  }else{
    while (r-l>1){
      mid=(l+r+1)/2;
      if (a[i]*a[mid] <= trg) r=mid;
      else l=mid;
    }
    if (r<=i) return n-r-1;
    else return n-r;
  }
}

int main(void){
  int n,i;
  ll a[200010],k;
  cin >> n >> k;
  for (i=0;i<n;i++) cin >> a[i];
  sort(a,a+n);
  
  ll l,r,mid,s;
  l=-1e18;
  r=1e18;
  while (r-l>1){
    mid=(l+r)/2;
    s=0;
    for (i=0;i<n;i++){
      s+=binary_search(n,a,i,mid);
    }
    s/=2;
    if (s>=k) r=mid;
    else l=mid;
  }
  
  cout << r << endl;
  
  return 0;
}