#include<bits/stdc++.h>
//ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);
//clock_t start=clock();clock_t end=clock();cout<<(double)(end-start)/CLOCKS_PER_SEC<<endl;
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef unsigned int ui;
typedef pair<int,int> pii;
typedef pair<pii,int> ppii;
typedef pair<int,pii> pipi;
typedef pair<ll,ll> pll;
typedef pair<pll,ll> ppll;
typedef pair<ll,pll> plpl;
typedef tuple<ll,ll,ll> tl;
ll mod=1000000007;
ll mod2=998244353;
ll mod3=1000003;
ll mod4=998244853;
ll inf=1LL<<60;
long double pi=3.141592653589793238462643383279L;
double eps=1e-12;
#define rep(i,m,n) for(ll i=m;i<n;i++)
#define rrep(i,n,m) for(ll i=n;i>=m;i--)
#define srep(itr,st) for(auto itr=st.begin();itr!=st.end();itr++)
int dh[4]={1,-1,0,0};
int dw[4]={0,0,1,-1};
int ddh[8]={-1,-1,-1,0,0,1,1,1};
int ddw[8]={-1,0,1,-1,1,-1,0,1};
ll gcd(ll a,ll b){
    if(a<b)swap(a,b);
    if(b==0)return a;
    if(a%b==0)return b;
    return gcd(b,a%b);
}
ll Pow(ll n,ll k){
    ll ret=1;
    ll now=n;
    while(k>0){
        if(k&1)ret*=now;
        now*=now;
        k/=2;
    }
    return ret;
}
ll beki(ll n,ll k,ll md){
  ll ret=1;
  ll now=n;
  while(k>0){
    if(k%2==1){
      ret*=now;
      ret%=md;
    }
    now*=now;
    now%=md;
    k/=2;
  }
  return ret;
}
ll gyaku(ll n,ll md){
  return beki(n,md-2,md);
}
int main(){
    ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);
    ll n;cin>>n;
    ll k;cin>>k;
    ll a[n];
    vector<ll> v,w;
    ll z=0;
    rep(i,0,n){
        cin>>a[i];
        if(a[i]>=0)v.push_back(a[i]);
        else w.push_back(-a[i]);
        if(a[i]==0)z++;
    }
    sort(v.begin(),v.end());
    sort(w.begin(),w.end());
    ll hu=(v.size()-z)*w.size();
    ll se=n*(n-1)/2-hu-z;
    
    ll u=1000000000000000001;
    ll d=0;
    ll tt=0;
    if(hu>=k){
        tt=1;
    }
    else if(hu+z>=k){
        cout<<0<<endl;
        return 0;
    }
    if(tt==0){
        k-=hu;
        k-=w.size()*z;
    }
    //cout<<k<<endl;
    while(u-d>1){
        ll mid=(u+d)/2;
        ll sum=0;
        if(tt==0){
            rep(i,0,v.size()){
                if(v[i]==0){
                    sum+=v.size()-i-1;
                    continue;
                }
                ll r=mid/v[i];
                if(mid%v[i]!=0)r++;
                ll y=lower_bound(v.begin(),v.end(),r)-v.begin();
                //if(mid==13)cout<<y<<" ";
                sum+=max((ll)0,y-(i+1));
            }
           // cout<<endl;
            rep(i,0,w.size()){
                ll r=mid/w[i];
                if(mid%w[i]!=0)r++;
                ll y=lower_bound(w.begin(),w.end(),r)-w.begin();
                sum+=max((ll)0,y-(i+1));
            }
            //if(mid<=21)cout<<sum<<" "<<mid<<endl;
            if(sum>=k)u=mid;
            else d=mid;
        }
        else{
            rep(i,0,v.size()){
                if(v[i]==0){
                    //sum+=w.size();
                    continue;
                }
                ll r=mid/v[i];
                r++;
                ll y=lower_bound(w.begin(),w.end(),r)-w.begin();
                sum+=w.size()-y;
            }
            //cout<<mid<<" "<<sum<<endl;
            if(sum>=k)d=mid;
            else u=mid;
        }
    }
    if(tt==1)cout<<-u<<endl;
    else cout<<d<<endl;
}




Measured memory_bytes: 3700