  Program Main

    Implicit None

    Integer, Allocatable :: A(:) 
    Integer(8)           :: i,j,N
    Logical              :: eq

    eq = .False.
    N  = 0
    Read(*,*) N
    Allocate (A(N)); A(:) = 0.0d0 
    Read(*,*)(A(i),i=1,N)

    Check:Do i = 1,N-1
             Do j = i+1,N
                If (A(i) == A(j)) then
                   eq = .True.
                   Exit Check
                Endif
             Enddo
          Enddo Check


    If (.not.eq) then
       Write(*,"(a)")"YES"
    Else
       Write(*,"(a)")"NO"
    Endif

    Deallocate(A)

  End Program
