#include <algorithm>
#include <bitset>
#include <complex>
#include <deque>
#include <iostream>
#include <istream>
#include <iterator>
#include <map>
#include <queue>
#include <set>
#include <stack>
#include <string>
#include <vector>
#include <tuple>
#include <iomanip>
#include <climits>
using namespace std;

typedef long long ll;
typedef unsigned long long ull;
//typedef pair<ll, ll> P;
#define rep(i, n) for(ll i = 0; i < (n); i++)
#define revrep(i, n) for(ll i = (n)-1; i >= 0; i--)
#define pb push_back
#define f first
#define s second
#define chmin(x, y) x = min(x, y);
#define chmax(x, y) x = max(x, y);

//const ll INFL = LLONG_MAX;//10^18 = 2^60
const ll INFL = 1LL<<61;
//const int INF = INT_MAX;
const ll INF = 1 << 30;//10^9
ll MOD = 1000000007;
//ll MOD = 998244353;

vector<ll> dy = {0, 1, 0, -1, 1, 1, -1, -1, 0};
vector<ll> dx = {1, 0, -1, 0, 1, -1, 1, -1, 0};

void pres(double A, ll x = 10){cout << fixed << setprecision(x) << A << endl;}
void BinarySay(ll x, ll y = 60){rep(i, y) cout << (x>>(y-1-i) & 1); cout << endl;}
ll cnt_bit(ll x){return __builtin_popcountll(x);}

ll pow_long(ll x, ll k){
  ll res = 1;
  while(k > 0){
    if(k % 2) res *= x;
    x *= x; k /= 2;
  }
  return res;
}

ll pow_mod(ll x, ll k){
  ll res = 1;
  while(k > 0){
    if(k % 2){
      res *= x; res %= MOD;
    }
    x *= x; x %= MOD;
    k /= 2;
  }
  return res;
}

ll inverse(ll x){return pow_mod(x, MOD - 2);};

ll gcd(ll a, ll b){
    if(b == 0) return a;
    return gcd(b, a % b);
}

ll lcm(ll x, ll y){
  ll res = x / gcd(x, y);
  res *= y;
  return res;
};

//コンビネーション
const int MAXcomb = 200010;
ll fac[MAXcomb], finv[MAXcomb], inv[MAXcomb];
//facはn!,finvは1/n!
//invは逆元
void COMinit(){
    fac[0] = fac[1] = 1;
    finv[0] = finv[1] = 1;
    inv[1] = 1;
    for(int i = 2; i < MAXcomb; i++){
        fac[i] = fac[i-1] * i % MOD;
        inv[i] = MOD - inv[MOD%i] * (MOD/i) % MOD;
        finv[i] = finv[i-1] * inv[i] % MOD;
    }
}
ll comb(int n, int k){
    if(n < k) return 0;
    if(n < 0 || k < 0) return 0;
    return fac[n] * finv[k] % MOD * finv[n-k] % MOD;
}

const int MAXkai = 200010;
ll kai_memo[MAXkai];
ll kai(ll N){
  if(kai_memo[N] != 0) return kai_memo[N];
  if(N <= 1) return 1;
  return kai_memo[N] = N * kai(N-1) % MOD;
}


ll N, K;
ll zero;
vector<ll> P, M, A;

bool can(ll x){
  ll res = 0;
  if(x > 0){
    //P, P
    rep(i, P.size()){
      if(P[0] * P[i] > x) continue;
      ll ok = 0, ng = P.size();
      while(ng - ok > 1){
        ll mid = (ok + ng) / 2;
        if(P[i] * P[mid] <= x) ok = mid;
        else ng = mid;
      }
      res += ok + 1;
    }
    //M, M
    rep(i, M.size()){
      if(M[0] * M[i] > x) continue;
      ll ok = 0, ng = M.size();
      while(ng - ok > 1){
        ll mid = (ok + ng) / 2;
        if(M[i] * M[mid] <= x) ok = mid;
        else ng = mid;
      }
      res += ok + 1;
    }
    rep(i, P.size()){
      if(P[i] * P[i] <= x) res--;
    }
    rep(i, M.size()){
      if(M[i] * M[i] <= x) res--;
    }
    res /= 2;

    res += P.size() * M.size();
    res += zero * (P.size() + M.size());
    res += zero * (zero - 1) / 2;
  }else if(x < 0){
    //P, M
    rep(i, P.size()){
      if(M.size() == 0) continue;
      if(-P[i] * M.back() > x) continue;
      ll ok = M.size() - 1, ng = -1;
      while(ok - ng > 1){
        ll mid = (ok + ng) / 2;
        if(-P[i] * M[mid] <= x) ok = mid;
        else ng = mid;
      }
      res += M.size() - ok;
    }
  }else{
    res += P.size() * M.size();
    res += zero * (P.size() + M.size());
    res += zero * (zero - 1) / 2;
  }
  return res >= K;
}

void solve(){
  cin >> N >> K;
  rep(i, N){
    ll a;
    cin >> a;
    if(a > 0) P.pb(a);
    else if(a < 0) M.pb(-a);
    else zero++;
    A.pb(a);
  }
  sort(A.begin(), A.end());
  sort(P.begin(), P.end());
  sort(M.begin(), M.end());
  ll ok = INFL, ng = -INFL;
  while(ok - ng > 1){
    ll mid = (ng + ok) / 2;
    if(can(mid)) ok = mid;
    else ng = mid;
  }
  cout << ok << endl;
}


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


Measured memory_bytes: 4468