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)

let () =
    let n = read_int () in
    let arr = Array.init n (fun _ -> Scanf.scanf " %d" (fun a -> a)) in
    Array.sort compare arr;
    let rec loop i prev =
        if i = n then "YES" else
            if arr.(i) = prev then "NO" else loop (i + 1) arr.(i)
    in
    loop 1 arr.(0) |>  print_endline