#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include <stack>
#include <queue>
#include <cmath>
#include <tuple>
#include <cstdio>
#include <bitset>
#include <sstream>
#include <iterator>
#include <numeric>
#include <map>
#include <cstring>
#include <set>
#include <functional>
#include <iomanip>

using namespace std;

//#define DEBUG_ //!!提出時にコメントアウト!!
#ifdef DEBUG_
	#define dump(x)  cerr << #x << " = " << (x) << endl;
#else
	#define dump(x)  ;
#endif

#define equals(a,b) (fabs((a)-(b)) < EPS)
#define FOR(i,a,b) for(int i=(a);i<(b);++i)
#define REP(i,n)  FOR(i,0,n)
#define SZ(x) ((int)(x).size())
#define pb push_back
#define eb emplace_back

//#define int long long

typedef long long LL;
typedef vector<int> VI;
typedef vector<LL> VL;
typedef vector<VI> VVI;
typedef vector<string> VS;
typedef pair<int, int> PII;
typedef pair<LL, LL> PLL;

template<class T>bool chmax(T &a, const T &b) { if (a<b) { a=b; return 1; } return 0; }
template<class T>bool chmin(T &a, const T &b) { if (b<a) { a=b; return 1; } return 0; }

template <typename T>
std::string printVector(const std::vector<T> &data)
{
    std::stringstream ss;
    std::ostream_iterator<T> out_it(ss, ", ");
    ss << "[";
    std::copy(data.begin(), data.end() - 1, out_it);
    ss << data.back() << "]";
    return ss.str();
}

template <typename T>
void print_array(const T &ary, int size){
    REP(i,size){
        cout << ary[i] << " ";
    }
    cout << endl;
}

const int MOD = 1e9+7;
const LL LINF = 1001002003004005006ll;
const int INF = 1001001001;
const double EPS = (1e-10);

signed main(int argc, char const *argv[])
{
    cin.tie(0);
    ios::sync_with_stdio(false);
    cout << setprecision(12);

    LL N,K; cin >> N >> K;
    VL A(N);
    REP(i,N) cin >> A[i];
    sort(A.begin(),A.end());


    LL r = 1e18 + 10;
    LL l = -1e18 - 10;
    while(r-l > 1){
        LL mid = (r+l) / 2; // mid以下に何個あるか
        LL acc = 0;
        dump(mid)
        REP(i,N){
            if(A[i] == 0){
                if(mid < 0) acc += 0;
                else acc += N-i-1;
                dump(acc)
            }
            else if(A[i] > 0){
                if(mid <= 0) ;
                else{
                    LL cap = mid / A[i];
                    dump(cap)
                    acc += upper_bound(A.begin()+i+1, A.end(), cap) - A.begin()-i-1;
                    dump(acc)
                }
            }else{
                if(mid == 0){
                    acc += A.end() - lower_bound(A.begin()+i+1,A.end(), 0);
                }
                else if(mid < 0){
                    LL cap = mid / A[i];
                    if(mid % A[i] != 0) cap++;
                    acc += A.end() - lower_bound(A.begin()+i+1, A.end(), cap);
                }else{
                    LL cap = mid / A[i];
                    acc += A.end() - lower_bound(A.begin()+i+1, A.end(),cap);
                    dump(cap)
                    dump(acc)
                }
            }
        }
        dump(acc)
        if(acc < K){
            l = mid;
        }else if(acc >= K){
            r = mid;
        }else{
            //cout << mid << endl;
            //return 0;
        }
    }
    cout << r << endl;



}


Measured memory_bytes: 1792