#pragma GCC optimize ("Ofast")
#include<bits/stdc++.h>
using namespace std;
void *wmem;
char memarr[96000000];
template<class T> inline void walloc1d(T **arr, int x, void **mem = &wmem){
  static int skip[16] = {0, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1};
  (*mem) = (void*)( ((char*)(*mem)) + skip[((unsigned long long)(*mem)) & 15] );
  (*arr)=(T*)(*mem);
  (*mem)=((*arr)+x);
}
template<class T1> void sortA_L(int N, T1 a[], void *mem = wmem){
  sort(a, a+N);
}
inline void rd(int &x){
  int k;
  int m=0;
  x=0;
  for(;;){
    k = getchar_unlocked();
    if(k=='-'){
      m=1;
      break;
    }
    if('0'<=k&&k<='9'){
      x=k-'0';
      break;
    }
  }
  for(;;){
    k = getchar_unlocked();
    if(k<'0'||k>'9'){
      break;
    }
    x=x*10+k-'0';
  }
  if(m){
    x=-x;
  }
}
inline void rd(long long &x){
  int k;
  int m=0;
  x=0;
  for(;;){
    k = getchar_unlocked();
    if(k=='-'){
      m=1;
      break;
    }
    if('0'<=k&&k<='9'){
      x=k-'0';
      break;
    }
  }
  for(;;){
    k = getchar_unlocked();
    if(k<'0'||k>'9'){
      break;
    }
    x=x*10+k-'0';
  }
  if(m){
    x=-x;
  }
}
inline void wt_L(char a){
  putchar_unlocked(a);
}
inline void wt_L(long long x){
  int s=0;
  int m=0;
  char f[20];
  if(x<0){
    m=1;
    x=-x;
  }
  while(x){
    f[s++]=x%10;
    x/=10;
  }
  if(!s){
    f[s++]=0;
  }
  if(m){
    putchar_unlocked('-');
  }
  while(s--){
    putchar_unlocked(f[s]+'0');
  }
}
int N;
int A[200000];
long long K;
long long ps;
long long ms;
long long p[200000];
long long m[200000];
int main(){
  wmem = memarr;
  int i;
  int j;
  long long res;
  long long cnt;
  rd(N);
  rd(K);
  {
    int Lj4PdHRW;
    for(Lj4PdHRW=(0);Lj4PdHRW<(N);Lj4PdHRW++){
      rd(A[Lj4PdHRW]);
    }
  }
  for(i=(0);i<(N);i++){
    if(A[i] >= 0){
      p[ps++] = A[i];
    }
    else{
      m[ms++] = -A[i];
    }
  }
  sortA_L(ps, p);
  sortA_L(ms, m);
  long long RZTsC2BF;
  long long FmcKpFmN;
  long long xr20shxY;
  RZTsC2BF = -1000000000000000000LL;
  FmcKpFmN = 1000000000000000000LL;
  while(RZTsC2BF < FmcKpFmN){
    if((RZTsC2BF + FmcKpFmN)%2==0){
      xr20shxY = (RZTsC2BF + FmcKpFmN) / 2;
    }
    else{
      xr20shxY = (RZTsC2BF + FmcKpFmN - 1) / 2;
    }
    cnt = 0;
    if(xr20shxY >= 0){
      cnt += ps * ms;
      j = ps - 1;
      for(i=(0);i<(ps);i++){
        while(j > i && p[i] * p[j] > xr20shxY){
          j--;
        }
        if(j <= i){
          break;
        }
        cnt += j - i;
      }
      j = ms - 1;
      for(i=(0);i<(ms);i++){
        while(j > i && m[i] * m[j] > xr20shxY){
          j--;
        }
        if(j <= i){
          break;
        }
        cnt += j - i;
      }
    }
    else{
      j = ms;
      for(i=(0);i<(ps);i++){
        while(j > 0 && p[i] * m[j-1] >= -xr20shxY){
          j--;
        }
        cnt += ms - j;
      }
    }
    if(cnt >= K){
      FmcKpFmN = xr20shxY;
    }
    else{
      RZTsC2BF = xr20shxY + 1;
    }
  }
  res =FmcKpFmN;
  wt_L(res);
  wt_L('\n');
  return 0;
}
// cLay varsion 20200214-1

// --- original code ---
// int N, A[2d5]; ll K;
// 
// ll ps, ms;
// ll p[2d5], m[2d5];
// 
// {
//   int i, j;
//   ll res, cnt;
//   rd(N,K,A(N));
//   rep(i,N) if[A[i] >= 0, p[ps++] = A[i], m[ms++] = -A[i]];
//   sortA(ps, p);
//   sortA(ms, m);
// 
//   res = bsearch_min[ll,x,-1d18,1d18][
//     cnt = 0;
//     if(x >= 0){
//       cnt += ps * ms;
// 
//       j = ps - 1;
//       rep(i,ps){
//         while(j > i && p[i] * p[j] > x) j--;
//         if(j <= i) break;
//         cnt += j - i;
//       }
// 
//       j = ms - 1;
//       rep(i,ms){
//         while(j > i && m[i] * m[j] > x) j--;
//         if(j <= i) break;
//         cnt += j - i;
//       }
//     } else {
//       j = ms;
//       rep(i,ps){
//         while(j > 0 && p[i] * m[j-1] >= -x) j--;
//         cnt += ms - j;
//       }
//     }
//   ](cnt >= K);
// 
//   wt(res);
// }


Measured memory_bytes: 3840