Problem:
Score : 300 points

Problem Statement

Given is a sequence of integers A_1, A_2, ..., A_N.
If its elements are pairwise distinct, print YES; otherwise, print NO.

Constraints

2 ≤ N ≤ 200000

1 ≤ A_i ≤ 10^9

All values in input are integers.

Input

Input is given from Standard Input in the following format:

N
A_1 ... A_N

Output

If the elements of the sequence are pairwise distinct, print YES; otherwise, print NO.

Sample Input 1

5
2 6 1 4 5

Sample Output 1

YES

The elements are pairwise distinct.

Sample Input 2

6
4 1 3 1 6 2

Sample Output 2

NO

The second and fourth elements are identical.

Sample Input 3

2
10000000 10000000

Sample Output 3

NO

Solution in Haskell (GHC 7.10.3) (judge verdict: Time Limit Exceeded)

module Main where

import Data.List

toInt :: String -> Int
toInt s = read s :: Int

anySame :: Eq a => [a] -> Bool
anySame = f []
 where
  f seen (x : xs) = x `elem` seen || f (x : seen) xs
  f seen []       = False

main :: IO ()
main = do
  getLine
  l <- getLine
  let ll = map toInt $ words l
  putStrLn $ if anySame $ sort ll then "NO" else "YES"