#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const char sp = ' ';

int N;
ll K, A[200000], L, R;

int main() {
	cin >> N >> K;
	for (int i = 0; i < N; i++) {
		cin >> A[i];
	}
	sort(A, A + N);
	L = -2e18;
	R = 2e18;
	while (L + 1 != R) {
		ll M = (L + R) / 2;
		ll cnt = 0;
		for (int i = 0; i < N; i++) {
			if (A[i] < 0) {
				int l, r;
				l = i;
				r = N;
				while (l + 1 != r) {
					int m = (l + r) / 2;
					if (A[i] * A[m] <= M) {
						r = m;
					}
					else {
						l = m;
					}
				}
				cnt += N - r;
			}
			else {
				int l, r;
				l = i;
				r = N;
				while (l + 1 != r) {
					int m = (l + r) / 2;
					if (A[i] * A[m] <= M) {
						l = m;
					}
					else {
						r = m;
					}
				}
				cnt += l - i;
			}
		}
		if (cnt < K)L = M;
		else R = M;
	}
	cout << R << endl;
}