Please explain how B = a(p-1)+b and b = B%(p-1)?

I am not able to get it. If you could explain with some easy example, it would be helpful.

sory i didnt get your Q. can u please explain what you are trying to ask and from where ? any video or blog …

Fermat’s little theorem states that if p is a prime number, then for any integer a, the number a^p – a is an integer multiple of p.
Special Case: If a is not divisible by p, Fermat’s little theorem is equivalent to the statement that a p-1-1 is an integer multiple of p.

example
P = an integer Prime number
a = an integer which is not multiple of P
Let a = 2 and P = 17

According to Fermat’s little theorem
2 17 - 1 ≡ 1 mod(17)
we got 65536 % 17 ≡ 1
that mean (65536-1) is an multiple of 17

for proof of little fermate theorem read this…
https://primes.utm.edu/notes/proofs/FermatsLittleTheorem.html

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