#include<bits/stdc++.h>
#include<ext/pb_ds/assoc_container.hpp>
#include<ext/pb_ds/tree_policy.hpp>

#define ll long long
#define ull unsigned long long
#define pii pair<int,int>
#define xx first
#define yy second
#define sci(n) scanf("%d",&n)
#define scii(n,m) scanf("%d%d",&n,&m)
#define sciii(n,m,w) scanf("%d%d%d",&n,&m,&w)
#define scl(n) scanf("%lld",&n)
#define scll(n,m) scanf("%lld%lld",&n,&m)
#define sclll(n,m,w) scanf("%lld%lld%lld",&n,&m,&w)
#define pf(a)   printf("%d\n",a)
#define CASE(a) printf("Case %d: ",a)
#define dbg(i) printf("yo %d\n", i)
#define endl '\n'
#define pi acos(-1)
#define mem(a,b) memset(a,b,sizeof(a))
#define SQR(a) (a)*(a)
#define all(v) v.begin(),v.end()
#define pb push_back
#define pri priority_queue<int>
#define rev_pri priority_queue<int,vector<int>,greater<int> >
#define IOS ios_base::sync_with_stdio(false);cin.tie(NULL);cout.tie(NULL);
#define mod 1000000007
#define inf INT_MAX
#define eps 1e-9

using namespace __gnu_pbds;
using namespace std;

//int dx[] = {0,1,0,-1,1,1,-1,-1};
//int dy[] = {1,0,-1,0,1,-1,-1,1};

//ll ncr(ll n,ll r){if(n==r)return 1;if(r==1)return n;if(dp[n][r]!=-1)return dp[n][r];return dp[n][r]=ncr(n-1,r)+ncr(n-1,r-1);}

// bit manipulations

//bool checkbit(int mask,int bit){return mask & (1<<bit);}
//int setbit(int mask,int bit){ return mask  (1<<bit) ; }
//int clearbit(int mask,int bit){return mask & ~(1<<bit);}
//int togglebit(int mask,int bit){return mask ^ (1<<bit);}

template <typename T> T BigMod (T b,T p,T m){if (p == 0) return 1;if (p%2 == 0){T s = BigMod(b,p/2,m);return ((s%m)*(s%m))%m;}return ((b%m)*(BigMod(b,p-1,m)%m))%m;}
template <typename T> T ModInv (T b,T m){return BigMod(b,m-2,m);}
template <typename T> T in(){char ch;T n = 0;bool ng = false;while (1){ch = getchar();if (ch == '-'){ng = true;ch = getchar();break;}if (ch>='0' && ch<='9')     break;}while (1){n = n*10 + (ch - '0');ch = getchar();if (ch<'0' || ch>'9')   break;}return (ng?-n:n);}
template <typename T> T POW(T B,T P){ if(P==0) return 1; if(P&1) return B*POW(B,P-1);  else return SQR(POW(B,P/2));}
template <typename T> T Bigmod(T b,T p,T m){ if(p==0) return 1; else if (!(p&1)) return SQR(Bigmod(b,p/2,m)) % m;else return ((b % m) * Bigmod(b,p-1,m)) % m;}
template <typename T> T Dis(T x1,T y1,T x2, T y2){return sqrt( SQR(x1-x2) + SQR(y1-y2) );}
template <typename T> T Angle(T x1,T y1,T x2, T y2){ return atan( double(y1-y2) / double(x1-x2));}
template <typename T> T DIFF(T a,T b) { T d = a-b;if(d<0)return -d;else return d;}
template <typename T> T ABS(T a) {if(a<0)return -a;else return a;}
template <typename T> T gcd(T a,T b){if(a<0)return gcd(-a,b);if(b<0)return gcd(a,-b);return (b==0)?a:gcd(b,a%b);}
template <typename T> T lcm(T a,T b) {if(a<0)return lcm(-a,b);if(b<0)return lcm(a,-b);return a*(b/gcd(a,b));}
template <typename T> T euclide(T a,T b,T &x,T &y) {if(a<0){T d=euclide(-a,b,x,y);x=-x;return d;}   if(b<0){T d=euclide(a,-b,x,y);y=-y;return d;}   if(b==0){x=1;y=0;return a;}else{T d=euclide(b,a%b,x,y);T t=x;x=y;y=t-(a/b)*y;return d;}}
template <typename T> void ia (T a[],int n){for (int i=0; i<n; i++) cin >> a[i];}
template <typename T> void pa (T a[],int n){for (int i=0; i<n-1; i++) cout << a[i] << " ";cout << a[n-1] << endl;}
template <typename T> ll isLeft(T a,T b,T c) { return (a.x-b.x)*(b.y-c.y)-(b.x-c.x)*(a.y-b.y);}

template<typename T>
using ordered_set=tree<T,null_type,less<T>,rb_tree_tag,tree_order_statistics_node_update>;

///********************************MY CODE STARTS HERE********************************///


#define mxn 100005

vector<ll>  pos,neg;

ll cnt_neg(ll x,ll val){

       ll lo = 0LL , hi = (ll)pos.size() - 1LL , res = pos.size();

       while(lo <= hi){
           ll mid = (lo + hi) / 2LL;

           ll product = x * pos[mid];
           if(product > val) lo = mid + 1LL;
           else{
               res = mid;
              hi = mid - 1LL;

           }

       }
       return (ll)pos.size() - res;


}


ll cnt_pos(ll i,ll val){

       ll lo = i + 1LL , hi = (ll)pos.size() - 1 , res = i;
       ll x = pos[i];

       while(lo <= hi){
           ll mid = (lo + hi) / 2LL;

           ll product = x * pos[mid];
           if(product > val) hi = mid - 1;
           else{
               res = mid;
               lo = mid + 1;

           }

       }
       return res - i;


}

ll cnt_neg_2(ll i,ll val){

       ll lo = i + 1 , hi = (ll)neg.size() - 1 , res = (ll)neg.size();
       ll x = neg[i];

       while(lo <= hi){
           ll mid = (lo + hi) / 2;

           ll product = x * neg[mid];
           if(product > val) lo = mid + 1;
           else{
               res = mid;
               hi = mid - 1;

           }

       }
       return (ll)neg.size() - res;


}




int main(){
       //IOS;

     ll n , k;
     cin >> n >> k;
     ll zero = 0;

     for(int i = 0;i < n;i++){
        ll x;
        cin >> x;
        if(x == 0) zero++;
         if(x < 0) neg.pb(x);
        else      pos.pb(x);

     }

     //cout << neg.size() << " " << pos.size() <<endl;
     sort(all(pos));
     sort(all(neg));


     ll lo = -1000000000000000000 , hi = 1000000000000000000 , res = -1;

     while(lo <= hi){
        ll mid = (lo + hi) / 2;
      // ll mid = -6;
      //cout << mid << endl;
        ll cnt = 0;


         //if(mid == 0){
          //   cnt += ((zero - 1) * zero ) / 2 + (n - pos.size() - zero) * zero;
        // }
         if(mid < 0){
           for(ll i = 0;i < (ll)neg.size();i++){
              cnt += cnt_neg(neg[i],mid);
           }


        }else{
            // cout << "ji" << mid << endl;

           for(ll i = 0;i < (ll)pos.size() - 1;i++){
              cnt += cnt_pos(i,mid);
           }
           //cout << cnt << endl;
           for(int i = 0;i < (ll)neg.size() - 1;i++){
              cnt += cnt_neg_2(i,mid);

           }
            cnt += (ll)(neg.size()) * (ll)pos.size();


        }
        //cout << cnt << endl;

        if(cnt < k){
            lo = mid + 1;

        }else{
           res = mid;
           hi = mid - 1;
        }

     }


      cout << res << endl;


return 0;}




Measured memory_bytes: 2548