import Data.List
import Data.Ord
import Data.Char
import Data.Ratio
import Data.Maybe

main = do
  n <- readLn :: IO Int
  print $ head [x|x<-[n,n-1..1], isSquare x==True]

isSquare :: Int -> Bool
isSquare n = m * m == n
  where m = intSqrt(n)
intSqrt :: Int -> Int
intSqrt n = floor (sqrt (fromIntegral n))