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: Accepted)

(defun solve (n a)
  (let ((hash (make-hash-table)))
    (loop for x in a
          if (gethash x hash)
          do (return "NO")
          else
          do (setf (gethash x hash) t)
          finally (return "YES"))))

#-swank
(let* ((n (read))
       (a (loop repeat n collect (read))))
  (format t "~A~%" (solve n a)))