#include <cstdio>
#include <cstring>
#include <iostream>
#include <algorithm>
using namespace std;

typedef long long ll;

const int N=2e5+7;
ll n,k,a[N],b[N],c[N],po,ne;

bool check(ll x) {
	int p=ne;ll ret=0;
	for (int i=1;i<=ne;i++) {
		while (p>=1&&b[i]*b[p]<x) p--;
		ret+=p;
	}
	p=1;
	for (int i=po;i>=1;i--) {
		while (p<=po&&c[i]*c[p]<x) p++;
		ret+=po-p+1;
	}
	p=po;
	for (int i=1;i<=n;i++) if (a[i]*a[i]>=x) ret--;
	ret/=2;
	for (int i=ne;i>=1;i--) {
		while (p>=1&&b[i]*c[p]<x) p--;
		ret+=p;
	}
	return n*(n-1)/2-ret>=k;
}

int main()
{
	scanf("%lld%lld",&n,&k);
	for (int i=1;i<=n;i++) scanf("%lld",&a[i]);
	sort(a+1,a+n+1);
	for (int i=1;i<=n;i++) if (a[i]<0) b[++ne]=a[i];else c[++po]=a[i];
	ll l=-1e18,r=1e18;
	while (l<r) {
		ll mid=(l+r) >> 1;
		if (check(mid)) r=mid;
		else l=mid+1;
	}
	printf("%lld\n",l-1);
	return 0;
}