#pragma GCC optimize("O3")
#pragma GCC target("avx")
#pragma GCC optimize("unroll-loops")
#define _GLIBCXX_DEBUG
#include <bits/stdc++.h>
using namespace std;
#define LL long long
#define DB double
#define ST string
#define BS bitset
#define VE vector
#define VL vector<LL>
#define VP vector<pair<LL,LL>>
#define VVL vector<vector<LL>>
#define PQ priority_queue
#define PQS priority_queue<LL,vector<LL>,greater<LL>>
#define PB push_back
#define POB pop_back
#define PF push_front
#define POF pop_front
#define EB emplace_back
#define MP make_pair
#define TS to_string
#define TU to_ullong
#define FOR(i,a,n) for(i=a;i<n;i++)
#define rep(i,n) FOR(i,0,n)
#define ALL(a) a.begin(),a.end()
#define RALL(a) a.rbegin(),a.rend()
#define SORT(a) sort(ALL(a))
#define REV(a) reverse(ALL(a))
#define UB(a,n) *upper_bound(ALL(a),n)
#define LB(a,n) *lower_bound(ALL(a),n)
#define INF 1145141919810364364
#define PI 3.14159265358979
#define MOD 1000000007
//#define MOD 998244353
#define ERR 0.00000001
//#define ERR 0.00000000000001
#define NUM 200010
#define FAST cin.tie(0);ios::sync_with_stdio(false)

void Yn(LL a){if(a)printf("Yes\n");else printf("No\n");}
void YN(LL a){if(a)printf("YES\n");else printf("NO\n");}
LL pwmn(LL a,LL n){LL ans=1;while(ans<a)ans*=n;return ans;}
LL GCD(LL a,LL b){LL c=1,tmp=max(a,b);b=min(a,b);a=tmp;while(c!=0){c=a%b;a=b;b=c;}return a;}
LL LCM(LL a,LL b){return a*b/GCD(a,b);}
int lcmp(const void* a,const void* b){if(*(LL*)a>*(LL*)b)return 1;if(*(LL*)a<*(LL*)b)return -1;return 0;}
int lcmpr(const void* a,const void* b){if(*(LL*)a>*(LL*)b)return -1;if(*(LL*)a<*(LL*)b)return 1;return 0;}
int ccmp(const void* a,const void* b){return *(char*)a-*(char*)b;}
int ccmpr(const void* a,const void* b){return *(char*)b-*(char*)a;}
int scmp(const void* a,const void* b){return strcmp((char*)a,(char*)b);}
int scmpr(const void* a,const void* b){return strcmp((char*)b,(char*)a);}
LL mod(LL a,LL m){if(a<0)return a%m+m;else return a%m;}
LL DIV(LL a,LL d){LL m=MOD,x=1,y=0,k;while(m){k=d/m;d-=k*m;swap(m,d);x-=k*y;swap(x,y);}return mod(a*mod(x,MOD),MOD);}
LL POW(LL a,LL n){LL ans=1;while(n>0){if(n&1)ans=ans*a%MOD;a=a*a%MOD;n>>=1;}return ans;}
LL fact[NUM],finv[NUM],inv[NUM];
void comi(){LL i;fact[0]=fact[1]=1;finv[0]=finv[1]=1;inv[1]=1;FOR(i,2,NUM){fact[i]=fact[i-1]*i%MOD;inv[i]=MOD-inv[MOD%i]*(MOD/i)%MOD;finv[i]=finv[i-1]*inv[i]%MOD;}}
LL com(LL n,LL k){if(n<k||n<0||k<0)return 0;return fact[n]*(finv[k]*finv[n-k]%MOD)%MOD;}
bool cmps(pair<LL,LL> a,pair<LL,LL> b){if(a.second!=b.second)return a.second<b.second;return a.first<b.first;}

int main(){
  FAST;
  LL i,ans=0,N,K,M,Z,P,mn,mx,md,a,n;
  cin>>N>>K;
  VL A(N),m,z,p;
  rep(i,N)cin>>A[i];
  SORT(A);
  rep(i,N){
    if(A[i]<0)m.EB(A[i]);
    else if(A[i]==0)z.EB(A[i]);
    else p.EB(A[i]);
  }
  REV(m);
  M=m.size(),Z=z.size(),P=p.size();
  if(K<=M*P){
    mn=-INF,mx=0;
    while(mx-mn>1){
      md=(mx+mn)/2;
      n=0,a=P-1;
      rep(i,M){
        while(a>0&&m[i]*p[a]<=md){
          if(m[i]*p[a-1]>md)break;
          else a--;
        }
        if(m[i]*p[a]<=md)n+=P-a;
        //cout<<a<<"  "<<i<<" "<<n<<endl;
      }
      //cout<<n<<" "<<md<<endl;
      if(n>=K)mx=md;
      else mn=md;
    }
    ans=mx;
  }else if(K>N*(N-1)/2-M*(M-1)/2-P*(P-1)/2){
    mn=0,mx=INF;
    while(mx-mn>1){
      md=(mx+mn)/2;
      n=0,a=M-1;
      rep(i,M-1){
        while(a>i+1&&m[i]*m[a]>=md){
          if(m[i]*m[a-1]<md)break;
          else a--;
        }
        if(a<=i)a=i+1;
        if(m[i]*m[a]>=md)n+=M-a;
        //cout<<a<<"  "<<i<<" "<<n<<endl;
      }
      //cout<<n<<" "<<md<<endl;
      a=P-1;
      rep(i,P-1){
        while(a>i+1&&p[i]*p[a]>=md){
          if(p[i]*p[a-1]<md)break;
          else a--;
        }
        if(a<=i)a=i+1;
        if(p[i]*p[a]>=md)n+=P-a;
        //cout<<a<<"  "<<i<<" "<<n<<endl;
      }
      //cout<<n<<" "<<md<<endl;
      if(N*(N-1)/2-n>=K)mx=md;
      else mn=md;
    }
    ans=mn;
  }
  cout<<ans<<endl;
}


Measured memory_bytes: 4468