Possible to measure 12.6v battery with arduino input?

so have 3s 800mah use power arduino uno, @ same time use 1 of analog pins monitor voltage. possible? also, know maximum current arduino input can handle 40 ma , i'm scared hooking fry board. there way can calculate how current flow through if connect powered lipo @ 12.6v uno (would ohm's law right track? if there resistance value arduino's input?).

thanks in advance help.

with attached circuit, voltage @ "a0" one-third of battery voltage.

> > > analog input must not greater a-ref (and must not greater 5v)

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