=9999*(1-1/1986)
=9999*1-9999/1986
=9999-3333/662
=9999-(5+23/662)
=9994-23/662
=9993+(1-23/662)
=9993+639/662
=9993又662分之639
=9999*(1-1/1986)
=9999*1-9999/1986
=9999-3333/662
=9999-(5+23/662)
=9994-23/662
=9993+(1-23/662)
=9993+639/662
=9993又662分之639