program exam
  implicit none
  integer :: n, c, i
  integer(8),allocatable :: a(:), b(:), p(:)
  integer(8) :: pmax, d, y
  read(*,*) n
  allocate(a(n), b(n), p(n))
  read(*,*) a
  read(*,*) b
  if (sum(a) < sum(b)) then
     write(*,*) -1
     stop
  end if
  
  p = a - b
  c = 0
  
  do i = 1, n
     if (p(i) < 0) then
        c = c + 1
        d = d + abs(p(i)) !だめの総和
     end if
  end do
  !もともと受からなかったかず
  if (c == 0) then
     write(*,*) 0
     stop
  end if
  
  call heapsort(p)

  do i = n, 1, -1
     c = c + 1
     d = d - p(i)
     if (d <= 0) then
        exit
     end if
  end do
  write(*,*) c
  
  stop
     
contains
    
subroutine heapsort(array)
  implicit none
  double precision,intent(inout) :: array(1:n)
  integer ::i,k,j,l
  double precision :: t

  n=size(array)
  
  if(n.le.0)then
     write(6,*)"Error, at heapsort"; stop
  endif
  if(n.eq.1)return

  l=n/2+1
  k=n
  do while(k.ne.1)
     if(l.gt.1)then
        l=l-1
        t=array(L)
     else
        t=array(k)
        array(k)=array(1)
        k=k-1
        if(k.eq.1) then
           array(1)=t
           exit
        endif
     endif
     i=l
     j=l+l
     do while(j.le.k)
        if(j.lt.k)then
           if(array(j).lt.array(j+1))j=j+1
        endif
        if (t.lt.array(j))then
           array(i)=array(j)
           i=j
           j=j+j
        else
           j=k+1
        endif
     end do
     array(i)=t
  end do
  return
end subroutine heapsort
end program exam
