program main
  implicit none
  integer*8::B,N,upper,total,i
  integer*8::C(10)
  read *,B,N
  if(N.eq.1) then
     print '(a)',"0"
     return
  end if

  read *,C(1:N)
  upper = (SUM(C(1:N))+B)/N
  total = 0
  do i=1,N
     total = total + ABS(C(i) - upper)
  end do
  print '(i0)', total
end program main