#include <bits/stdc++.h>
using namespace std;

#define lli long long int
#define REP(i,s,n) for(int i=s;i<n;i++)
#define NUM 2520
#define INF (1LL<<50)
#define DEBUG 0
#define mp(a,b) make_pair(a,b)
#define SORT(V) sort(V.begin(),V.end())
#define PI (3.141592653589794)
#define TO_STRING(VariableName) # VariableName
#define LOG(x) if(DEBUG)cout<<TO_STRING(x)<<"="<<x<<" "<<endl;
#define LOG2(x,y) if(DEBUG)cout<<TO_STRING(x)<<"="<<x<<" "<<TO_STRING(y)<<"="<<y<<endl;
#define LOG3(x,y,z) if(DEBUG)cout<<TO_STRING(x)<<"="<<x<<" "<<TO_STRING(y)<<"="<<y<<" "<<TO_STRING(z)<<"="<<z<<endl;
#define LOG4(w,x,y,z) if(DEBUG)cout<<TO_STRING(w)<<"="<<w<<" "<<TO_STRING(x)<<"="<<x<<" "<<TO_STRING(y)<<"="<<y<<" "<<TO_STRING(z)<<"="<<z<<endl;

template<class T>bool chmax(T & a, const T & b) { if (a < b) { a = b; return 1; } return 0; }
template<class T>bool chmin(T& a, const T& b) { if (b < a) { a = b; return 1; } return 0; }

void func(long long N, long long K, std::vector<long long> A){

    vector<lli> minus,plus,zero;
    REP(i,0,N){
        if(A[i]<0)minus.push_back(A[i]);
        else if(A[i]==0)zero.push_back(A[i]);
        else plus.push_back(A[i]);
    }

    lli minusNum = (minus.size()*plus.size());
    lli plusNum = (minus.size()*(minus.size()-1)/2 + (plus.size()*(plus.size()-1)/2));
    lli zeroNum = N*(N-1)/2 - (minusNum + plusNum);

    LOG3(minusNum,zeroNum,plusNum);
    if(K <= minusNum){

        K = minusNum -K;
        K++;

        REP(i,0,minus.size())minus[i] *= -1;
        
        SORT(minus);
        SORT(plus);

        lli small = 0;
        lli large = 1e18;
        while(small+1 < large){
            lli middle = (small+large)/2;
            lli sum = 0;
            LOG3(small,middle,large);
            REP(i,0,minus.size()){
                lli target = middle/minus[i];
                lli cnt = (lli)(upper_bound(plus.begin(),plus.end(),target) - plus.begin());
                LOG3(i,target,cnt);
                sum += cnt;
            }
            LOG4(small,middle,large,sum);
            if(sum >= K){
                large = middle;
            }
            else{
                small = middle;
            }
        }
        cout<<-large<<endl;

    }
    else if(K <= (minusNum + zeroNum)) {
        cout<<0<<endl;
        return;
    }
    else{
        K -= (minusNum+zeroNum);
        REP(i,0,minus.size())minus[i] *= -1;
        
        SORT(minus);
        SORT(plus);

        lli small = 0;
        lli large = 1e18;
        while(small+1 < large){
            lli middle = (small+large)/2;
            lli sum = 0;
            LOG3(small,middle,large);
            REP(i,0,minus.size()){
                lli target = middle/minus[i];
                lli cnt = (lli)(upper_bound(minus.begin(),minus.end(),target) - minus.begin());
                cnt = max(0LL,cnt-i-1);
                sum += cnt;
            }
            REP(i,0,plus.size()){
                lli target = middle/plus[i];
                lli cnt = (lli)(upper_bound(plus.begin(),plus.end(),target) - plus.begin());
                cnt = max(0LL,cnt-i-1);
                LOG3(i,target,cnt);
                sum += cnt;
            }
            LOG4(small,middle,large,sum);
            if(sum >= K){
                large = middle;
            }
            else{
                small = middle;
            }
        }
        cout<<large<<endl;
    }

}

int main(){
    // cout << fixed << setprecision(5);

    long long N;
    scanf("%lld",&N);
    long long K;
    scanf("%lld",&K);
    std::vector<long long> A(N);
    for(int i = 0 ; i < N ; i++){
        scanf("%lld",&A[i]);
    }
    func(N, K, std::move(A));
    return 0;
}


Measured memory_bytes: 4084