#define _USE_MATH_DEFINES
#include <algorithm>
#include <bitset>
#include <cassert>
#include <cctype>
#include <clocale>
#include <cmath>
#include <cstdlib>
#include <ctime>
#include <deque>
#include <fstream>
#include <functional>
#include <iomanip>
#include <iostream>
#include <iterator>
#include <list>
#include <map>
#include <queue>
#include <regex>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <tuple>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <vector>

using namespace std;

#define IOS ios::sync_with_stdio(false); cin.tie(0);
#define FOR(i, s, n) for(int i = (s), i##_len=(n); i < i##_len; ++i)
#define FORS(i, s, n) for(int i = (s), i##_len=(n); i <= i##_len; ++i)
#define VFOR(i, s, n) for(int i = (s); i < (n); ++i)
#define VFORS(i, s, n) for(int i = (s); i <= (n); ++i)
#define REP(i, n) FOR(i, 0, n)
#define REPS(i, n) FORS(i, 0, n)
#define VREP(i, n) VFOR(i, 0, n)
#define VREPS(i, n) VFORS(i, 0, n)
#define RFOR(i, s, n) for(int i = (s), i##_len=(n); i >= i##_len; --i)
#define RFORS(i, s, n) for(int i = (s), i##_len=(n); i > i##_len; --i)
#define RREP(i, n) RFOR(i, n, 0)
#define RREPS(i, n) RFORS(i, n, 0)
#define ALL(v) (v).begin(), (v).end()
#define SORT(v) sort(ALL(v))
#define RSORT(v) sort(ALL(v), greater<decltype(v[0])>())
#define SZ(x) ((int)(x).size())
#define PB push_back
#define EB emplace_back
#define MP make_pair
#define MT make_tuple
#define BIT(n) (1LL<<(n))
#define UNIQUE(v) v.erase(unique(ALL(v)), v.end())

using ld = long double;
using ll = long long;
using ui = unsigned int;
using ull = unsigned long long;
using Pi_i = pair<int, int>;
using Pll_ll = pair<ll, ll>;
using VB = vector<bool>;
using VC = vector<char>;
using VD = vector<double>;
using VI = vector<int>;
using VLL = vector<ll>;
using VS = vector<string>;
using VSH = vector<short>;
using VULL = vector<ull>;

const int MOD = 1000000007;
const int INF = 1000000000;
const int NIL = -1;
const double EPS = 1E-10;

template<class T, class S>
bool chmax(T &a, const S &b){
    if(a < b){
        a = b; return true;
    }
    return false;
}
template<class T, class S>
bool chmin(T &a, const S &b){
    if(b < a){
        a = b; return true;
    }
    return false;
}


int main(){
    ll N, K; cin >> N >> K;
    ll n, z = 0, p;
    VLL neg, pos;
    REP(i, N){
        int A; cin >> A;
        if(A < 0) neg.PB(A);
        if(A == 0) ++z;
        if(A > 0) pos.PB(A);
    }
    n = neg.size(); p = pos.size();
    SORT(neg); SORT(pos);
    if(n*p >= K){//答えは負の数, [lt, rt[
        ll lt = neg[0]*pos[p-1], rt = 0;
        while(lt+1 < rt){
            ll mid = (lt+rt)/2;
            int j = 0;
            ll cnt = 0;
            REP(i, n){
                while(j<p && neg[i]*pos[j]>=mid) ++j;
                if(j == p) break;
                cnt += p - j;
            }
            if(cnt < K) lt = mid;
            else rt = mid;
        }
        cout << lt << endl;
        return 0;
    }else if(n*p + z*(n+p) + z*(z-1)/2 >= K){
        cout << 0 << endl;
        return 0;
    }else{//答えは正の数, ]lt, rt]
        ll more = N*(N-1)/2 - K + 1;
        ll lt = 0, rt = 1;
        if(n) rt = neg[0]*neg[0] + 1;
        if(p) chmax(rt, pos[p-1]*pos[p-1]+1);
        while(lt+1 < rt){
            ll mid = (lt+rt)/2;
            ll cnt = 0, sqcnt = 0;
            int j = 0;
            RREP(i, p-1){
                if(pos[i]*pos[i] > mid) ++sqcnt;
                while(j<p && pos[i]*pos[j]<=mid) ++j;
                if(j == p) break;
                cnt += p - j;
            }
            j = n - 1;
            REP(i, n){
                if(neg[i]*neg[i] > mid) ++sqcnt;
                while(j>=0 && neg[i]*neg[j]<=mid) --j;
                if(j == -1) break;
                cnt += j + 1;
            }
            cnt = (cnt-sqcnt)/2;
            if(cnt < more) rt = mid;
            else lt = mid;
        }
        cout << rt << endl;
    }
    return 0;
}


Measured memory_bytes: 2420