#include<iostream>
#include<cstdio>
#include<algorithm>
#include<cstring>
using namespace std;
typedef long long ll;
const int N=2e5+10;
ll n,k,l,r,a[N];
void pt(ll a,ll b,ll c)
{
	printf("a[%d]:%lld num:%lld\n",a,b,c);
}
ll cal(ll x)
{
	ll num=0;
	if(x>=0)
	{
		for(int i=0;i<n;++i)
		{
			if(a[i]==0)num+=n;
			else if(a[i]>0)num+=upper_bound(a,a+n,x/a[i])-a;
			else num+=n-(lower_bound(a,a+n,x/a[i])-a);
		}
	}
	else
	{
		for(int i=0;i<n;++i)
		{
			if(a[i]==0)continue;
			if(a[i]>0)num+=upper_bound(a,a+n,(x-a[i]+1)/a[i])-a;
			else num+=n-(lower_bound(a,a+n,(x+a[i]+1)/a[i])-a);
		}
	}
	for(int i=0;i<n;++i)
		if(a[i]*a[i]<=x)num--;
	num/=2;
	return num;
}
int main()
{
	scanf("%lld%lld",&n,&k);
	for(int i=0;i<n;++i)
	scanf("%lld",&a[i]);
	sort(a,a+n);
	l=-1e18,r=1e18;
	while(l<=r)
	{
		ll mid=(l+r)/2;
		if(cal(mid)>=k)r=mid-1;
		else l=mid+1;
	}
	printf("%lld\n",l);
	return 0;
}