error -39 on update 8.1.3.iphone 4s

my i phone 4s was updated with update 8.1.3 now i can not open i can not login

it shows only i tunes icon and the window box recommend to connect to itunes to continue update , i did but it stopped with an error -39 what is that mean , is it mean that the update can not be continued or finshed and i have to choice the second option which is restore to factory . what can i do as next step