#include<bits/stdc++.h>
using namespace std;
int n;
long long k,cl,cr,cm,l,r,m,tot,a[2000100],INF=1e9+1;
long long Get(){
	for(int i=0;i<n;i++){
		if(a[i]<0){
			l=-1,r=n;
			while(l+1<r){
				m=(l+r)/2LL;
				if(a[i]*a[m]<cm) r=m;
				else l=m;
			}
			tot+=(long long)(n)-r;
		}
		else{
			l=-1,r=n;
			while(l+1<r){
				m=(l+r)/2LL;
				if(a[i]*a[m]<cm) l=m;
				else r=m;
			}
			tot+=r;
		}
		if((a[i]*a[i])<cm) tot-=1LL;
	}
	tot/=2LL;
}
int main(){
	#ifdef FILIN
		#ifndef DavidDesktop
			freopen(FILIN,"r",stdin);
			freopen(FILOUT,"w",stdout);
		#endif
	#endif
	ios::sync_with_stdio(false);
	cin.tie(NULL);
	cout.tie(NULL);
	cin>>n>>k;
	for(int i=0;i<n;i++)
		cin>>a[i];
	sort(a,a+n);
	INF*=INF,cl=-INF,cr=INF;
	while(cl+1<cr){
		cm=(cl+cr)/2LL,tot=0LL;
		if(Get()<k) cl=cm;
		else cr=cm;
		if(tot<k) cl=cm;
		else cr=cm;
	}
	cout<<cl<<endl;
	return 0;
}
