Figuring out which FCM tokens are expired from a firebase response with several registration ids -

firebase rest endpoint push notifications lets send message several people @ once passing tokens through "registration_ids" array instead of "to". when response comes looks this:

{    "multicast_id":000000000000000000,    "success":1,    "failure":4,    "canonical_ids":0,    "results":[       {          "error":"notregistered"       },       {          "error":"notregistered"       },       {          "error":"notregistered"       },       {          "error":"notregistered"       },       {          "message_id":"0:0000000000000000%a0a0a0aaa0a0a0aa"       }    ] } 

how supposed correlate notregistered errors particular token sent to?

the results in same order specified them in request. last token valid.