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)

(let* ((n (read))
       (as (make-array n :element-type 'fixnum)))
  (loop for i from 0 below n
        do (setf (aref as i) (read)))
  (setf as (sort as #'>))
  (princ (loop for i from 1 below n
               do (when (= (aref as i) (aref as (- i 1)))
                    (return "NO"))
               finally (return "YES")))
  (terpri))