Provide your best answer for the following math problem. Give ONLY the answer, no other words or explanation.
For example:

Answer: <most likely answer, as short as possible; not a complete sentence, just the answer!>.

The problem is: what is the unit digit in [ ( 6273 ) ^ 1793 x ( 625 ) ^ 317 x ( 341 ) ^ 491 ] ?
0
3.