#include<iostream>
#include<string>
#include<cstdio>
#include<vector>
#include<cmath>
#include<algorithm>
#include<functional>
#include<iomanip>
#include<queue>
#include<ciso646>
#include<random>
#include<map>
#include<set>
#include<bitset>
#include<stack>
#include<unordered_map>
#include<utility>
#include<cassert>
#include<complex>
#include<numeric>
using namespace std;

//#define int long long
typedef long long ll;

typedef unsigned long long ul;
typedef unsigned int ui;
const ll mod = 1000000007;
const ll INF = (1e+18) + 7;
typedef pair<int, int>P;
#define stop char nyaa;cin>>nyaa;
#define rep(i,n) for(int i=0;i<n;i++)
#define per(i,n) for(int i=n-1;i>=0;i--)
#define Rep(i,sta,n) for(int i=sta;i<n;i++)
#define rep1(i,n) for(int i=1;i<=n;i++)
#define per1(i,n) for(int i=n;i>=1;i--)
#define Rep1(i,sta,n) for(int i=sta;i<=n;i++)
#define all(v) (v).begin(),(v).end()
typedef pair<ll, ll> LP;
typedef long double ld;
typedef pair<ld, ld> LDP;
const ld eps = 1e-6;
const ld pi = acos(-1.0);
//typedef vector<vector<ll>> mat;
typedef vector<int> vec;

ll mod_pow(ll a, ll n) {
	ll res = 1;
	while (n) {
		if (n & 1)res = res * a%mod;
		a = a * a%mod; n >>= 1;
	}
	return res;
}

struct modint {
	ll n;
	modint() :n(0) { ; }
	modint(ll m) :n(m) {
		if (n >= mod)n %= mod;
		else if (n < 0)n = (n%mod + mod) % mod;
	}
	operator int() { return n; }
};
bool operator==(modint a, modint b) { return a.n == b.n; }
modint operator+=(modint &a, modint b) { a.n += b.n; if (a.n >= mod)a.n -= mod; return a; }
modint operator-=(modint &a, modint b) { a.n -= b.n; if (a.n < 0)a.n += mod; return a; }
modint operator*=(modint &a, modint b) { a.n = ((ll)a.n*b.n) % mod; return a; }
modint operator+(modint a, modint b) { return a += b; }
modint operator-(modint a, modint b) { return a -= b; }
modint operator*(modint a, modint b) { return a *= b; }
modint operator^(modint a, int n) {
	if (n == 0)return modint(1);
	modint res = (a*a) ^ (n / 2);
	if (n % 2)res = res * a;
	return res;
}

ll inv(ll a, ll p) {
	return (a == 1 ? 1 : (1 - p * inv(p%a, a)) / a + p);
}
modint operator/(modint a, modint b) { return a * modint(inv(b, mod)); }

const int max_n = 500;
modint fact[max_n], factinv[max_n];
void init_f() {
	fact[0] = modint(1);
	for (int i = 0; i < max_n - 1; i++) {
		fact[i + 1] = fact[i] * modint(i + 1);
	}
	factinv[max_n - 1] = modint(1) / fact[max_n - 1];
	for (int i = max_n - 2; i >= 0; i--) {
		factinv[i] = factinv[i + 1] * modint(i + 1);
	}
}
modint comb(int a, int b) {
	if (a < 0 || b < 0 || a < b)return 0;
	return fact[a] * factinv[b] * factinv[a - b];
}

int dx[4] = { 0,1,0,-1 };
int dy[4] = { 1,0,-1,0 };

void solve() {
	int n; ll k;
	cin >> n >> k;
	vector<ll> a(n);
	vector<ll> pos, neg;
	ll c0 = 0;
	rep(i, n) {
		cin >> a[i];
		if (a[i] == 0)c0++;
		else if (a[i] > 0)pos.push_back(a[i]);
		else neg.push_back(a[i]);
	}
	ll ss = c0 * (n - c0) + c0 * (c0 - 1) / 2;
	ll x = (ll)pos.size()*neg.size();
	if (x >= k) {
		ll le = -1, ri = INF;
		rep(i, neg.size())neg[i] = -neg[i];
		sort(all(neg));
		sort(all(pos));
		while (ri - le > 1) {
			ll m = (le + ri) / 2;
			ll num = 0;
			rep(i, pos.size()) {
				ll rest = (m+pos[i]-1) / pos[i];
				num +=neg.end()- lower_bound(all(neg), rest);
			}
			if (num >= k) {
				le = m;
			}
			else {
				ri = m;
			}
		}
		cout << -le << endl;
	}
	else if (k <= x + ss) {
		cout << 0 << endl;
	}
	else {
		k -= x+ss;
		rep(i, neg.size())neg[i] = -neg[i];
		sort(all(neg));
		sort(all(pos));
		ll le = -1, ri = INF;
		while (ri - le > 1) {
			ll m = (le + ri) / 2;
			ll num = 0;
			rep(i, pos.size()) {
				ll rest = m / pos[i];
				num += upper_bound(all(pos), rest) - pos.begin();
				if (pos[i] * pos[i] <= m)num--;
			}
			rep(i, neg.size()) {
				ll rest = m / neg[i];
				num += upper_bound(all(neg), rest) - neg.begin();
				if (neg[i] * neg[i] <= m)num--;
			}
			//cout << m << " " << num << endl;
			num /= 2;
			if (num >= k) {
				ri = m;
			}
			else {
				le = m;
			}
		}
		cout << ri << endl;
	}
}


signed main() {
	ios::sync_with_stdio(false);
	cin.tie(0);
	cout << fixed << setprecision(10);
	//init_f(); init();
	//int t; cin >> t; rep(i, t)solve();
	//while(cin>>n,n)solve();
	solve();
	stop
		return 0;
}


Measured memory_bytes: 3956