program main

  implicit none

  integer    :: n
  integer(8),allocatable :: a(:)
  integer :: i, j 
  
  read(*,*) n
  allocate( a(n) )
  read(*,*) a

  call quicksort1( a, 1, n ) 
  
  j = 0 
  do i = 2, n
    if( a(i) == a(i-1) ) j = j + 1
  end do
  
  if ( j > 0 ) then
    print*, "NO" 
  else
    print*, "YES" 
  end if

end program main

recursive subroutine quicksort1(a, first, last)
  implicit none
  integer(8),intent(inout)::a(*)
  integer,intent(in)::first,last
  !
  ! Original
  ! https://gist.github.com/t-nissie/479f0f16966925fa29ea
  !
  integer(8)::x,t
  integer::i,j

  x = a((first+last)/2)
  i = first
  j = last
  do
     do while (a(i) < x)
        i=i+1
     end do
     do while (x < a(j))
        j=j-1
     end do
     if (i >= j) exit
     t = a(i)
     a(i) = a(j)
     a(j) = t
     i=i+1
     j=j-1
  end do
  if (first < i-1) call quicksort1(a, first, i-1)
  if (j+1 < last)  call quicksort1(a, j+1, last)

  return
end subroutine quicksort1
