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 Common Lisp (SBCL 1.1.14) (judge verdict: Time Limit Exceeded)

(defun splitat (c line)
  (labels ((rec (line acc)
				(let ((pos (position-if (lambda(cc) (char= c cc)) line)))
				  (if pos
					  (rec (subseq line (1+ pos)) (cons (subseq line 0 pos) acc))
					(nreverse (cons line acc))))))
	(rec line nil)))
(defun ff(n arr)
  (let ((sorted (sort arr #'<))
        (found nil))
    (dotimes (i (1- n))
      (if (= (elt sorted i) (elt sorted (1+ i)))
        (setq found t)))
    (if found "NO" "YES")))
(defun f(n arr)
  (let* ((sorted (sort arr #'<))
        (arr1 (subseq sorted 1)))
    (if (some #'= sorted arr1) "NO" "YES")))
(compile 'f)
(let* ((n (parse-integer (read-line nil nil)))
       (line1 (mapcar #'parse-integer (splitat #\space (read-line nil nil))))
       (arr (make-array (length line1) :initial-contents line1)))
  (format t "~A~%" (f n arr)))