{-# OPTIONS_GHC -O2 #-}
{-# LANGUAGE BangPatterns, CPP, FlexibleContexts, FlexibleInstances         #-}
{-# LANGUAGE KindSignatures, LambdaCase, MagicHash, MultiParamTypeClasses   #-}
{-# LANGUAGE MultiWayIf, OverloadedStrings, RecordWildCards                 #-}
{-# LANGUAGE ScopedTypeVariables, TupleSections, TypeFamilies, ViewPatterns #-}

import           Control.Applicative
import           Control.Exception
import           Control.Monad
import           Control.Monad.Primitive
import           Control.Monad.ST
import           Control.Monad.State.Strict
import           Data.Bool
import qualified Data.ByteString             as B
import qualified Data.ByteString.Builder     as B
import qualified Data.ByteString.Char8       as C
import qualified Data.ByteString.Internal    as B
import qualified Data.ByteString.Unsafe      as B
import           Data.Char
import qualified Data.Foldable               as F
import           Data.Function
import           Data.Functor.Identity
import qualified Data.IntMap.Strict          as IM
import qualified Data.IntSet                 as IS
import qualified Data.List                   as L
import qualified Data.Map.Strict             as M
import           Data.Monoid
import           Data.Ord
import           Data.Primitive.MutVar
import           Data.Ratio
import qualified Data.Set                    as S
import           Data.Tuple
import qualified Data.Vector                 as V
import qualified Data.Vector.Generic         as G
import qualified Data.Vector.Generic.Mutable as GM
import qualified Data.Vector.Mutable         as VM
import qualified Data.Vector.Unboxed         as U
import qualified Data.Vector.Unboxed.Mutable as UM
import           Debug.Trace
import           Foreign                     hiding (void)
import           GHC.Exts
import qualified System.IO                   as IO
import           Unsafe.Coerce

main :: IO ()
main = do
    [n, k] <- map read.words <$> getLine :: IO [Int]
    xycs <- U.unfoldrN n (runParser $ (,,) <$> double <*> double <*> double) <$> C.getContents
    print $ solve n k xycs

solve :: Int -> Int -> U.Vector (Double, Double, Double) -> Double
solve n k (U.toList -> xycs)
    = snd . goldenRatioSearchDownward low high $ \x ->
        snd . goldenRatioSearchDownward low high $ \y ->
            f x y
  where
    f x y = L.sort [ci*sqrt((xi-x)*(xi-x)+(yi-y)*(yi-y))|(xi, yi, ci) <- xycs] !! (k - 1)
    low = -1000.0
    high = 1000.0

double :: Parser Double
double = fromIntegral <$> int

phi :: Double
phi = 1.618033988749895
{-# INLINE phi #-}

resphi :: Double
resphi = 0.3819660112501051
{-# INLINE resphi #-}

mid1 :: Double -> Double -> Double
mid1 low high = (low * phi + high) * resphi
{-# INLINE mid1 #-}

mid2 :: Double -> Double -> Double
mid2 low high = (low + high * phi) * resphi
{-# INLINE mid2 #-}

eps :: Double
eps = 1e-8
{-# INLINE eps #-}

goldenRatioSearchDownward :: Double -> Double -> (Double -> Double) -> (Double, Double)
goldenRatioSearchDownward low high f = go 72 low x1 x2 high (f x1) (f x2)
   where
     !x1 = mid1 low high
     !x2 = mid2 low high
     go !n !x0 !x1 !x2 !x3 !fx1 !fx2
       | n == 0 || abs (x3 - x0) < eps = let !k = (x0 + x3) * 0.5
                                             !fk = f k
                                         in (k, fk)
       | fx1 < fx2 = let !x = mid1 x0 x2
                     in go (n - 1) x0 x x1 x2 (f x) fx1
       | otherwise = let !x = mid2 x1 x3
                     in go (n - 1) x1 x2 x x3 fx2 (f x)


-------------------------------------------------------------------------------
-- Utils
-------------------------------------------------------------------------------
rep :: Monad m => Int -> (Int -> m ()) -> m ()
rep !n = U.forM_ $ U.generate n id
{-# INLINE rep #-}
rev :: Monad m => Int -> (Int -> m ()) -> m ()
rev !n = U.forM_ $ U.iterateN n (subtract 1) (n - 1)
{-# INLINE rev #-}
infixl 8 `shiftRL`, `unsafeShiftRL`
shiftRL = unsafeShiftRL
{-# INLINE shiftRL #-}
unsafeShiftRL (I# x#) (I# i#) = I# (uncheckedIShiftRL# x# i#)
{-# INLINE unsafeShiftRL #-}
type Parser a = StateT C.ByteString Maybe a
runParser :: Parser a -> C.ByteString -> Maybe (a, C.ByteString)
runParser = runStateT
{-# INLINE runParser #-}
int :: Parser Int
int = coerce $ C.readInt . C.dropWhile isSpace
{-# INLINE int #-}
int1 :: Parser Int
int1 = fmap (subtract 1) int
{-# INLINE int1 #-}
char :: Parser Char
char = coerce C.uncons
{-# INLINE char #-}
byte :: Parser Word8
byte = coerce B.uncons
{-# INLINE byte #-}
