#include <bits/stdc++.h>
using namespace std;

typedef unsigned long long ull;
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef pair<double, double> pdd;
//const ull mod = 1e9 + 7;
const ll mod = 1e9 + 7;
#define REP(i,n) for(int i=0;i<(int)n;++i)

// debug
#define dump(x)  cerr << #x << " = " << (x) << endl;
#define debug(x) cerr << #x << " = " << (x) << " (L" << __LINE__ << ")" << " " << __FILE__ << endl;

template<class S, class T> ostream& operator << (ostream& os, const pair<S, T> v){
  os << "(" << v.first << ", " << v.second << ")"; return os;
}
template<class T> ostream& operator << (ostream& os, const vector<T> v){
  for(int i = 0; i < (int)v.size(); i++){if(i > 0){os << " ";} os << v[i];} return os;
}
template<class T> ostream& operator << (ostream& os, const vector<vector<T>> v){
  for(int i = 0; i < (int)v.size(); i++){if(i > 0){os << endl;} os << v[i];} return os;
}
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 (a>b) { a=b; return 1; } return 0; }

// conversion number to bit
string num2bit(ll num, ll len){
  string bit = "";
  REP(i, len){
    bit += char('0'+(num>>i & 1));
  }
  return bit;
}

ll N, K;
vector<ll> pos, neg;
ll z = 0;

ll count_neg(ll x){
	//正×負で絶対値がx以上になるものを探す
	ll res = 0;
	for(auto val: pos){

		//*
		ll ng = -1;
		ll ok = neg.size();
		while(ok-ng>1){
			ll md = (ok+ng)/2;
			if(val*neg[md]>=x) ok = md;
			else ng = md;
		}
		res += (ll)neg.size() - ok;
		//*/

		/*
		ll tmp = neg.end() - lower_bound(neg.begin(), neg.end(), (x+val-1)/val);
		res += tmp;
		//*/
	}
	return res;
}

ll count_pos(ll x){
	ll res = 0;

	// 負×負で絶対値がx以下になるものを探す
	REP(i, neg.size()){
		ll val = neg[i];

		//*
		ll ok = -1;
		ll ng = i;
		while(ng-ok>1){
			ll md = (ok+ng)/2;
			if(val*neg[md]<=x) ok = md;
			else ng = md;
		}
		res += ng;
		//*/

		/*
		ll tmp = upper_bound(neg.begin(), neg.begin()+i, x/val) -  neg.begin();
		res += tmp;
		//*/
	}

	// 正×正で絶対値がx以下になるものを探す
	REP(i, pos.size()){
		ll val = pos[i];

		//*
		ll ok = -1;
		ll ng = i;
		while(ng-ok>1){
			ll md = (ok+ng)/2;
			if(val*pos[md]<=x) ok = md;
			else ng = md;
		}
		res += ng;
		//*/

		/*
		ll tmp = upper_bound(pos.begin(), pos.begin()+i, x/val) -  pos.begin();
		res += tmp;
		//*/
	}

	return res;
}

ll count(ll x){
	ll res = 0;
	ll zeros = N*(N-1)/2 - (N-z)*(N-z-1)/2;

	if(x<0){
		res += count_neg(-x);
	}else if(x==0){
		res += count_neg(0);
		res += zeros;
	}else{
		res += count_neg(0);
		res += zeros;
		res += count_pos(x);
	}

	return res;
}

int main(){
    cin.tie(0);
    ios::sync_with_stdio(false);

    
    cin >> N >> K;
    vector<ll> A(N);
    REP(i, N) cin >> A[i];

    REP(i, N){
    	if(A[i]>0) pos.push_back(A[i]);
    	else if(A[i]==0) z++;
    	else neg.push_back(-A[i]);
    }
    sort(pos.begin(), pos.end());
    sort(neg.begin(), neg.end());

    //cout << pos << endl;
    //cout << neg << endl;

    const ll INF = (ll)1e18 + 5;

    ll ng = -INF;
    ll ok = INF;
    while(ok-ng>1){
    	ll md = (ok+ng)/2;
    	if(count(md)>=K) ok = md;
    	else ng = md;
    }

    cout << ok << endl;
    return 0;
}

Measured memory_bytes: 3956