program main
  implicit none
  integer*8::N,D,i,curr,next,total
  integer,allocatable::ashiba(:)
  read *,N,D
  allocate(ashiba(0:D))
  ashiba = 1
  curr = 0

  do i=1,D
     ashiba(curr) = 0
     total = (N-1)/D + total
     next = MOD(curr+(N/D+1)*D,N)

     if(ashiba(next).eq.0) exit
     curr = next
  end do
  print '(i0)',total
end program main