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 Fortran (gfortran v4.8.4) (judge verdict: Runtime Error)

program main
integer::i,n,k
integer,allocatable::a(:),b(:)
read(*,*)n
allocate(a(n))
	read(*,*)a(:)
    k=maxval(a)
allocate(b(k))
b=0
do i=1,n
	b(a(i))=b(a(i))+1
end do
if(maxval(b)==1)then
	print*,'YES'
else
	print*,'NO'
end if
end program main