program abc65
 implicit none
 integer(8)::N,ia,ib,ic,j=1
 integer(8),allocatable::a(:)
 read(*,*)N
 allocate(a(N))
 read(*,*)(a(ia),ia=1,N)
 do ib=1,N-1
  do ic=ib+1,N
   if(a(ib)==a(ic))then
    j=0
    goto 1
   end if
  end do
 end do
 1 if(j==0)then
    print'(a)',"NO"
   else
    print'(a)',"YES"
   end if
 deallocate(a)
end program abc65