#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);
}
void sortF_L(int N, unsigned A[], void *mem = wmem){
  int i;
  int m;
  int bt;
  unsigned *arr;
  unsigned c;
  int *sz;
  if(N < 256){
    sort(A, A+N);
    return;
  }
  bt = sizeof(unsigned) * 8;
  walloc1d(&arr, N, &mem);
  walloc1d(&sz, N, &mem);
  for(m=0;m<bt;m+=8){
    for(i=(0);i<(257);i++){
      sz[i] = 0;
    }
    for(i=(0);i<(N);i++){
      sz[ 1+((A[i]>>m)&255u) ]++;
    }
    for(i=(1);i<(257);i++){
      sz[i] += sz[i-1];
    }
    for(i=(0);i<(N);i++){
      c = ((A[i]>>m)&255u);
      arr[sz[c]++] = A[i];
    }
    swap(A, arr);
  }
}
void sortF_L(int N, int A[], void *mem = wmem){
  int i;
  int x;
  int y;
  int z;
  int *arr;
  unsigned *send;
  if(N < 256){
    sort(A, A+N);
    return;
  }
  send = (unsigned*)A;
  sortF_L(N, send, mem);
  if(A[0] < 0 || A[N-1] >= 0){
    return;
  }
  x = 0;
  y = N;
  while(x < y){
    z = (x+y) / 2;
    if(A[z] < 0){
      y = z;
    }
    else{
      x = z+1;
    }
  }
  walloc1d(&arr, N, &mem);
  z = 0;
  for(i=(x);i<(N);i++){
    arr[z++] = A[i];
  }
  for(i=(0);i<(x);i++){
    arr[z++] = A[i];
  }
  for(i=(0);i<(N);i++){
    A[i] = arr[i];
  }
}
void sortF_L(int N, unsigned long long A[], void *mem = wmem){
  int i;
  int m;
  int bt;
  unsigned long long *arr;
  unsigned c;
  int *sz;
  if(N < 512){
    sort(A, A+N);
    return;
  }
  bt = sizeof(unsigned long long) * 8;
  walloc1d(&arr, N, &mem);
  walloc1d(&sz, N, &mem);
  for(m=0;m<bt;m+=8){
    for(i=(0);i<(257);i++){
      sz[i] = 0;
    }
    for(i=(0);i<(N);i++){
      sz[ 1+((A[i]>>m)&255u) ]++;
    }
    for(i=(1);i<(257);i++){
      sz[i] += sz[i-1];
    }
    for(i=(0);i<(N);i++){
      c = ((A[i]>>m)&255u);
      arr[sz[c]++] = A[i];
    }
    swap(A, arr);
  }
}
void sortF_L(int N, long long A[], void *mem = wmem){
  int i;
  int x;
  int y;
  int z;
  long long *arr;
  unsigned long long *send;
  if(N < 512){
    sort(A, A+N);
    return;
  }
  send = (unsigned long long*)A;
  sortF_L(N, send, mem);
  if(A[0] < 0 || A[N-1] >= 0){
    return;
  }
  x = 0;
  y = N;
  while(x < y){
    z = (x+y) / 2;
    if(A[z] < 0){
      y = z;
    }
    else{
      x = z+1;
    }
  }
  walloc1d(&arr, N, &mem);
  z = 0;
  for(i=(x);i<(N);i++){
    arr[z++] = A[i];
  }
  for(i=(0);i<(x);i++){
    arr[z++] = A[i];
  }
  for(i=(0);i<(N);i++){
    A[i] = arr[i];
  }
}
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');
  }
}
template<class T> long long counterProdIsLT(int As, T A[], int Bs, T B[], T val){
  int i;
  int j;
  int ma = 0;
  int za = 0;
  int pa = 0;
  int mb = 0;
  int zb = 0;
  int pb = 0;
  long long res = 0;
  i = 0;
  while(i < As && A[i] < 0){
    i++;
  }
  ma = i;
  while(i < As && A[i] == 0){
    i++;
  }
  za = i - ma;
  pa = As - i;
  i = 0;
  while(i < Bs && B[i] < 0){
    i++;
  }
  mb = i;
  while(i < Bs && B[i] == 0){
    i++;
  }
  zb = i - mb;
  pb = Bs - i;
  if(val < 0){
    j = 0;
    for(i=(0);i<(pa);i++){
      while(j < mb && A[As-pa+i] * B[j] < val){
        j++;
      }
      res += j;
    }
    j = 0;
    for(i=(0);i<(pb);i++){
      while(j < ma && B[Bs-pb+i] * A[j] < val){
        j++;
      }
      res += j;
    }
  }
  else if(val == 0){
    res = (long long) ma * pb + (long long) pa * mb;
  }
  else{
    res = (long long) As * Bs - (long long) pa * pb - (long long) ma * mb;
    j = pb;
    for(i=(0);i<(pa);i++){
      while(j && A[As-pa+i] * B[Bs-pb+j-1] >= val){
        j--;
      }
      if(j==0){
        break;
      }
      res += j;
    }
    j = mb;
    for(i=(0);i<(ma);i++){
      while(j && A[ma-1-i] * B[mb-j] >= val){
        j--;
      }
      if(j==0){
        break;
      }
      res += j;
    }
  }
  return res;
}
int N;
long long A[200000];
long long K;
int main(){
  wmem = memarr;
  long long res;
  long long cnt;
  rd(N);
  rd(K);
  {
    int Lj4PdHRW;
    for(Lj4PdHRW=(0);Lj4PdHRW<(N);Lj4PdHRW++){
      rd(A[Lj4PdHRW]);
    }
  }
  sortF_L(N, A);
  long long e98WHCEY;
  long long cTE1_r3A;
  long long RZTsC2BF;
  e98WHCEY = -1000000000000000000LL;
  cTE1_r3A = 1000000000000000000LL;
  while(e98WHCEY < cTE1_r3A){
    int i;
    if((e98WHCEY + cTE1_r3A)%2==0){
      RZTsC2BF = (e98WHCEY + cTE1_r3A) / 2;
    }
    else{
      RZTsC2BF = (e98WHCEY + cTE1_r3A - 1) / 2;
    }
    cnt = counterProdIsLT(N,A,N,A,RZTsC2BF+1);
    for(i=(0);i<(N);i++){
      if(A[i]*A[i] <= RZTsC2BF){
        cnt--;
      }
    }
    cnt /= 2;
    if(cnt >= K){
      cTE1_r3A = RZTsC2BF;
    }
    else{
      e98WHCEY = RZTsC2BF + 1;
    }
  }
  res =cTE1_r3A;
  wt_L(res);
  wt_L('\n');
  return 0;
}
// cLay varsion 20200217-1

// --- original code ---
// int N; ll A[2d5], K;
// 
// {
//   ll res, cnt;
//   rd(N,K,A(N));
//   sortF(N, A);
// 
//   res = bsearch_min[ll,x,-1d18,1d18][
//     cnt = counterProdIsLT(N,A,N,A,x+1);
//     rep(i,N) if(A[i]*A[i] <= x) cnt--;
//     cnt /= 2;
//   ](cnt >= K);
// 
//   wt(res);
// }


Measured memory_bytes: 4352