local mfl = math.floor

local function comp(a, b)
  return a < b
end

local function lower_bound(ary, x, mul)
  local num = #ary
  if num == 0 then return 1 end
  if not comp(ary[1] * mul, x) then return 1 end
  if comp(ary[num] * mul, x) then return num + 1 end
  local min, max = 1, num
  while 1 < max - min do
    local mid = mfl((min + max) / 2)
    if comp(ary[mid] * mul, x) then
      min = mid
    else
      max = mid
    end
  end
  return max
end
local function upper_bound(ary, left, x, mul)
  local num = #ary
  if num == 0 then return 1 end
  if comp(x, ary[left] * mul) then return left end
  if not comp(x, ary[num] * mul) then return num + 1 end
  local min, max = left, num
  while 1 < max - min do
    local mid = mfl((min + max) / 2)
    if not comp(x, ary[mid] * mul) then
      min = mid
    else
      max = mid
    end
  end
  return max
end

local n, k = io.read("*n", "*n")
local t = {}
for i = 1, n do
  t[i] = 0LL + io.read("*n")
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
table.sort(minus)
table.sort(plus)
local ten9 = 1000000000LL
local minus_cnt = #minus * #plus
if k <= minus_cnt then
  local function solve(x)
    x = -x
    local cnt = 0
    for i = 1, #minus do
      local z = lower_bound(plus, x, minus[i])
      cnt = cnt + (#plus + 1 - z)
    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
  k = k - minus_cnt
  local function solveA(x)
    local cnt = 0
    for i = 1, #minus - 1 do
      local z = upper_bound(minus, i + 1, x, minus[i]) - 1
      cnt = cnt + (z - i)
    end
    for i = 1, #plus - 1 do
      local z = upper_bound(plus, i + 1, x, plus[i]) - 1
      cnt = cnt + (z - i)
    end
    return k <= cnt
  end
  local max = ten9 * ten9 + 1LL
  local min = -1LL
  while 1LL < max - min do
    local mid = (min + max) / 2LL
    if solveA(mid) then
      max = mid
    else
      min = mid
    end
  end
  local str = tostring(max):gsub("LL", "")
  print(str)
end
