#include <bits/stdc++.h>
using namespace std;
using ll  = long long;
using vl  = vector<ll>;

#define rep(i,n) for(int i = 0; i < (n); ++i)
#define rng(i,a,b) for(int i = (a); i < (b); ++i)
#define all(a) (a).begin(), (a).end()

int main() {
    ll N, K; cin >> N >> K;
    vl A(N);
    rep(i,N) cin >> A[i];
    sort(all(A));

    ll ng = 2e18, ok = -ng;
    while (ng - ok > 1) {
        ll x = (ok + ng) / 2, cnt = 0;
        rep(i,N) {
            if (A[i] < 0) cnt += N - (upper_bound(all(A), (long double)x/A[i]) - A.begin());
            if (A[i] > 0) cnt += lower_bound(all(A), (long double)x/A[i]) - A.begin();
            if (A[i] == 0 and x > 0) cnt += N;
            if (A[i]*A[i] < x) cnt--;
        }
        (cnt/2 < K ? ok : ng) = x;
    }
    cout << ok << endl;
    return 0;
}
