local mfl = math.floor
local function lower_bound(ary, x, right)
  local num = #ary
  if num == 0 then return 1 end
  if not (ary[1] < x) then return 1 end
  if (ary[right] < x) then return right + 1 end
  local min, max = 1, right
  while 1 < max - min do
    local mid = mfl((min + max) / 2)
    if (ary[mid] < x) then
      min = mid
    else
      max = mid
    end
  end
  return max
end
local g_tgt = 0LL
local function upper_bound(ary, left, right)
  local num = #ary
  if num == 0 then return 1 end
  if (g_tgt < ary[left] ) then return left end
  if not (g_tgt < ary[right] ) then return right + 1 end
  local min, max = left, right
  while 1 < max - min do
    local mid = mfl((min + max) / 2)
    if not (g_tgt < ary[mid] ) then
      min = mid
    else
      max = mid
    end
  end
  return max
end

local n, k = io.read("*n", "*n", "*l")
local t = {}
local str = io.read()
for s in str:gmatch("(-?%d+)") do
  table.insert(t, tonumber(s))
end
table.sort(t)
local plus_start_pos = n + 1
local minus, plus = {}, {}
for i = n, 1, -1 do
  if t[i] < 0 then
    table.insert(minus, -t[i])
  else
    table.insert(plus, t[i])
    plus_start_pos = i
  end
end
do
  local hn = math.floor(#plus / 2)
  for i = 1, hn do
    plus[i], plus[#plus + 1 - i] = plus[#plus + 1 - i], plus[i]
  end
end
local ten9 = 1000000000LL
local minus_cnt = #minus * #plus
if k <= minus_cnt then
  local mmi = math.min
  local function solve(x)
    x = -x
    local cnt = 0
    local right = #plus
    for i = 1, #minus do
      local dst = x / (0LL + minus[i])
      if x % minus[i] ~= 0 then dst = dst + 1 end
      local z = lower_bound(plus, dst, right)
      cnt = cnt + (#plus + 1 - z)
      if z == 1 then
        cnt = cnt + (#minus - i) * #plus
        break
      else
        right = mmi(z, #plus)
      end
    end
    return k <= cnt
  end
  local max = 1LL
  local min = -ten9 * ten9 - 1LL
  while 1LL < max - min do
    local mid = (min + max) / 2LL
    if solve(mid) then
      max = mid
    else
      min = mid
    end
  end
  local str = tostring(max):gsub("LL", "")
  print(str)
else
  local mmi = math.min
  k = k - minus_cnt
  local function solveA(x)
    local cnt = 0
    local right = #minus
    for i = 1, #minus - 1 do
      g_tgt = x / minus[i]
      local z = upper_bound(minus, i + 1, right) - 1
      cnt = cnt + (z - i)
      if z - i == 0 then break end
      right = mmi(z + 1, #minus)
    end
    right = #plus
    for i = 1, #plus - 1 do
      local z = 0
      if plus[i] == 0 then
        if x < 0 then
          z = i
        else
          z = right
        end
      else
        g_tgt = x / plus[i]
        z = upper_bound(plus, i + 1, right) - 1
      end
      cnt = cnt + (z - i)
      if z - i == 0 then break end
      right = mmi(z + 1, #plus)
    end
    return cnt
  end
  local max = ten9 * ten9 + 1LL
  local min = -1LL
  local mid = (min + max) / 2LL
  while 1LL < max - min do
    local r = solveA(mid)
    if max - min < 10LL then
      if k <= r then
        max = mid
      else
        min = mid
      end
      mid = (min + max) / 2LL
    else
      if k <= r then
        max = mid
        if k * 10 < r then
          mid = (min * 3 + max) / 4LL
        else
          mid = (min + max) / 2LL
        end
      else
        min = mid
        if r * 10 < k then
          mid = (min + max * 3) / 4LL
        else
          mid = (min + max) / 2LL
        end
      end
    end
  end
  local str = tostring(max):gsub("LL", "")
  print(str)
end
