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 Pascal (FPC 2.6.2) (judge verdict: Accepted)

Var  n,i,x:longint;
       a:array[0..1000000000] of boolean;
Begin{main}
  read(n);
  for i:=1 to n do
    begin
      read(x);
      if a[x] then begin write('NO');exit;end;
      a[x]:=true;
    end; 
    write('YES');
End.