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 OCaml (4.02.3) (judge verdict: Accepted)

open Batteries
let n = read_int ()
let a = read_line () |> String.split_on_char ' ' |> List.sort compare

let _ =
  let rec loop lst =
    match lst with
    | [] -> "YES"
    | first :: second :: rest -> if first = second then "NO" else loop (second :: rest)
    | first :: rest -> loop rest
  in loop a |> print_endline