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

hasDuplicate [] = False
hasDuplicate [_] = False
hasDuplicate (h:tail) = if h `elem` tail
                           then True
                           else hasDuplicate tail

main :: IO ()
main =
  (read :: String -> Int) <$> getLine >>= \n ->
  (map (read :: String -> Int) . words) <$> getLine >>= \arr ->
  if hasDuplicate arr
     then putStrLn "NO"
     else putStrLn "YES"