program main
	implicit none
    integer i,j,n,flag,l,k,tmp
    integer,allocatable :: a(:)
    
    flag=1 !distinct
    
    read(*,*) n
    allocate(a(n))
    read(*,*) (a(i),i=1,n)
    
    l=n/2+1
    k=n
    do while(k/=1)
      if(l>1)then
        l=l-1
        tmp=a(l)
      else
        tmp=a(k)
        a(k)=a(1)
        k=k-1
        if(k==1) then
           a(1)=tmp
           exit
        endif
     endif
     i=l
     j=l+l
     do while(j<=k)
        if(j<k)then
           if(a(j).lt.a(j+1))j=j+1
        endif
        if (tmp<a(j))then
           a(i)=a(j)
           i=j
           j=j+j
        else
           j=k+1
        endif
     enddo
     a(i)=tmp
  enddo
  write(*,*) a
  do i=1,n-1     
     if (a(i)==a(i+1)) then
        flag=0
        goto 99
     end if
  end do
99 continue
    if (flag==1) then
       write(*,'(a)') 'YES'
    else
       write(*,'(a)') 'NO'
    end if
end program main