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

int main() {
  long N, K;
  cin >> N >> K;
  vector<long> A(N);
  for (int i = 0; i < N; i++) cin >> A.at(i);
  sort(A.begin(), A.end());
  long L = -2e18, R = 2e18;
  while (R - L > 1) {
    long M = (L + R) / 2, cnt = 0;
    for (int i = 0; i < N; i++) {
      if (A.at(i) < 0) {
        int l = -1, r = N;
        while (r - l > 1) {
          int m = (l + r) / 2;
          (A.at(i) * A.at(m) < M) ? r = m : l = m;
        }
        cnt += N - r;
      } else {
        int l = -1, r = N;
        while (r - l > 1) {
          int m = (l + r) / 2;
          (A.at(i) * A.at(m) < M) ? l = m : r = m;
        }
        cnt += r;
      }
      if (A.at(i) * A.at(i) < M) cnt--;
    }
    (cnt / 2 < K) ? L = M : R = M;
  }
  cout << L << "\n";
}