//  Created by conan1024hao in 2020.
//  Copyright © 2020 conan1024hao. All rights reserved.
//  専用ライブラリです、自由にコピーして構いません。
//  感谢看我的代码！Wechat:conan1024hao Twitter/QQ:810396815
#pragma GCC optimize ("O3")
#include <iostream>
#include <iomanip>
#include <istream>
#include <ostream>
#include <sstream>
#include <iterator>
#include <vector>
#include <algorithm>
#include <queue>
#include <deque>
#include <list>
#include <stack>
#include <map>
#include <unordered_map>
#include <set>
#include <utility>
#include <cmath>
#include <cstdio>
#include <cstring>
#include <string>
#include <ctime>
#include <cctype>
#include <cstdlib>
#define IINF 10e8
#define INF 10e17
#define MOD 1000000007
#define mod 1000000007
#define rep(i, a, n) for (ll i = a; i < (ll)(n); i++)
#define Endl endl
#define fi first
#define se second
#define pb push_back
#define mp make_pair
#define eb emplace_back
#define mmax(x,y)(x>y?x:y)
#define mmin(x,y)(x<y?x:y)
#define chmax(x,y) x=mmax(x,y)
#define chmin(x,y) x=mmin(x,y)
#define all(x) (x).begin(),(x).end()
#define siz(x) (ll)(x).size()
#define PI acos(-1.0)
using namespace std;
//using Int=int_fast64_t;
typedef long long int ll;
typedef long long int LL;
typedef pair<ll,ll>Pll;
typedef pair<int,int>Pin;
long long GCD(long long a, long long b) { return b ? GCD(b, a%b) : a; }
long long LCM(long long a, long long b)  {return a/GCD(a,b)*b;}
int dx[4]={-1,0,1,0};
int dy[4]={0,-1,0,1};
char dir[4]={'u','l','d','r'};
ll cmp1(pair<ll,string>a,pair<ll,string> b){
        if(a.fi!=b.fi)
        return a.fi<b.fi;
        else
        return a.se<b.se;
}

//---------------------------------------------------------------------------
vector<ll>a,b;
ll n,k;
ll judge(ll v){
    ll res=0;
    for(ll i=0;i<n;i++){
        ll lb=-1,rb=n;
        if(a[i]<0){
            while(rb-lb>1){
                ll mid=(lb+rb)/2;
                if(a[i]*b[mid]>v)rb=mid;
                else lb=mid;
            }
            ll tmp;
            if(a[i]*a[i]<=v)tmp=0;
            else tmp=1;
            res+=lb+tmp;
        }
        else{
            while(rb-lb>1){
                ll mid=(lb+rb)/2;
                if(a[i]*a[mid]>v)rb=mid;
                else lb=mid;
            }
            ll tmp;
            if(a[i]*a[i]<=v)tmp=0;
            else tmp=1;
            res+=lb+tmp;
        }
    }
    return res/2;
}
//---------------------------------------------------------------------------
int main(){//問題をちゃんと見ろ!!!!!!!!!!!!!!!!!      llか??????????统一类型        memset()!!!!!!!!!!!!       ペナを減らせ!!!!!!!!!!!!!
    cin.tie(0);
    ios::sync_with_stdio(false);
    //-------------------------------
    cin>>n>>k;
    a.resize(n);
    for(ll i=0;i<n;i++)cin>>a[i];
    sort(all(a));
    for(ll i=0;i<n;i++)b.pb(a[i]);
    reverse(all(b));
    ll lb=-INF,rb=INF;
    while(rb-lb>1){
        ll mid=(rb+lb)/2;
        if(judge(mid)>=k)rb=mid;
        else lb=mid;
    }
    cout<<rb<<endl;
    //-------------------------------
    return 0;
}
//---------------------------------------------------------------------------






//99999999999995
// 31415  9  265358  9 7  9  323846264338327  9  5028841  9  71693  9  9  3755105820  9  74  9  445  9 2307816406286208  9  9  86280348253421170


Measured memory_bytes: 3956