Notice how 2^2 = 4 is one short of 5, so this means we can say 4/5 = 0 remainder 4 or we can write that "remainder 4" as "remainder -1" to say the same basic thing
Using modulus arithmetic, we can say...
2^2 = 4 = -1 (mod 5)
(2^2)^31 = (-1)^31 = -1 (mod 5)
2*(2^2)^31 = 2*(-1) (mod 5)
2^63 = -2 = 3 (mod 5)
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So the remainder of 2^63 divided by 5 is the value 3
Answer: 3
