#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <cmath>
#include <queue>
#include <stack>
#include <map>
#include <set>
#include <vector>
#include <iomanip>
#define ALL(x) (x).begin(), (x).end()
#define sz(a) int(a.size())
#define rep(i,x,n) for(int i=x;i<n;i++)
#define repd(i,x,n) for(int i=x;i<=n;i++)
#define pii pair<int,int>
#define pll pair<long long ,long long>
#define gbtb ios::sync_with_stdio(false),cin.tie(0),cout.tie(0)
#define MS0(X) memset((X), 0, sizeof((X)))
#define MSC0(X) memset((X), '\0', sizeof((X)))
#define pb push_back
#define mp make_pair
#define fi first
#define se second
#define eps 1e-6
#define chu(x) cout<<"["<<#x<<" "<<(x)<<"]"<<endl
#define du3(a,b,c) scanf("%d %d %d",&(a),&(b),&(c))
#define du2(a,b) scanf("%d %d",&(a),&(b))
#define du1(a) scanf("%d",&(a));
using namespace std;
typedef long long ll;
ll gcd(ll a, ll b) {return b ? gcd(b, a % b) : a;}
ll lcm(ll a, ll b) {return a / gcd(a, b) * b;}
ll powmod(ll a, ll b, ll MOD) { if (a == 0ll) {return 0ll;} a %= MOD; ll ans = 1; while (b) {if (b & 1) {ans = ans * a % MOD;} a = a * a % MOD; b >>= 1;} return ans;}
void Pv(const vector<int> &V) {int Len = sz(V); for (int i = 0; i < Len; ++i) {printf("%d", V[i] ); if (i != Len - 1) {printf(" ");} else {printf("\n");}}}
void Pvl(const vector<ll> &V) {int Len = sz(V); for (int i = 0; i < Len; ++i) {printf("%lld", V[i] ); if (i != Len - 1) {printf(" ");} else {printf("\n");}}}
inline long long readll() {long long tmp = 0, fh = 1; char c = getchar(); while (c < '0' || c > '9') {if (c == '-') fh = -1; c = getchar();} while (c >= '0' && c <= '9') tmp = tmp * 10 + c - 48, c = getchar(); return tmp * fh;}
inline int readint() {int tmp = 0, fh = 1; char c = getchar(); while (c < '0' || c > '9') {if (c == '-') fh = -1; c = getchar();} while (c >= '0' && c <= '9') tmp = tmp * 10 + c - 48, c = getchar(); return tmp * fh;}
const int maxn = 1000010;
const int inf = 0x3f3f3f3f;
/*** TEMPLATE CODE * * STARTS HERE ***/
ll k, n;
ll a[maxn];
std::vector<ll> v1, v2;
ll len1, len2;
std::vector<ll> v;
ll cnt = 0ll;
bool check(ll x)
{
    ll res = 0ll;
    if (x > 0)
    {
        for (auto y : v1)
        {
            res += lower_bound(ALL(v), (x + y - 1) / y)- v.begin();
            v.push_back(y);
        }
        v.clear();
        for (auto y : v2)
        {
            res += lower_bound(ALL(v), (x + y - 1) / y) - v.begin();
            v.push_back(y);
        }
        v.clear();
        res += cnt * (cnt - 1) / 2;
        res += 1ll * sz(v1) * sz(v2);
        res += cnt * (sz(v1) + sz(v2));
    } else if (x < 0)
    {
        x = -x;
        for (auto y : v1)
        {
            res += sz(v2) - (upper_bound(ALL(v2), x / y) - v2.begin());
        }
    } else
    {
        res += 1ll * sz(v1) * sz(v2);
    }
    return res < k;
}
int main()
{
    //freopen("D:\\code\\text\\input.txt","r",stdin);
    //freopen("D:\\code\\text\\output.txt","w",stdout);
    n = readll();
    k = readll();
    repd(i, 1, n)
    {
        a[i] = readll();
        if (a[i] > 0)
        {
            v1.push_back(a[i]);
        } else if (a[i] < 0)
        {
            v2.push_back(-a[i]);
        } else
        {
            cnt++;
        }
    }
    sort(ALL(v1));
    sort(ALL(v2));
    len1 = sz(v1);
    len2 = sz(v2);
    ll l = -1e18;
    ll r = 1e18;
    ll mid;
    ll ans;
    while (l <= r)
    {
        mid = (l + r) >> 1;
//        cout << mid << endl;
        if(mid==7)
        {
            mid=7;
        }
        if (check(mid))
        {
            l = mid + 1;
            ans = mid;
        } else
        {
            r = mid - 1;
        }
    }
//    cout << l << " " << mid << " " << r << endl;
    printf("%lld\n", ans );
    return 0;
}


Measured memory_bytes: 6256