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 a:array[0..200001] of longint;
    n,i:longint;p:boolean;
procedure sort(l,r:longint);
var
 i,j,t,mid:longint;
begin
 i:=l;j:=r;mid:=a[(i+j) div 2];
 repeat
  while a[i]<mid do inc(i);
  while a[j]>mid do dec(j);
  if i<=j then
   begin
    t:=a[i];a[i]:=a[j];a[j]:=t;
    inc(i);dec(j);
   end;
 until i>j;
 if i<r then sort(i,r);
 if j>l then sort(l,j);
end;
begin
 readln(n);
 for i:=1 to n do read(a[i]);
 sort(1,n);
 p:=false;
 for i:=2 to n do if a[i]=a[i-1] then p:=true;
 if p then writeln('NO')
  else writeln('YES');
end.