Hello Codeforces, recently, there was a contest on CSAcademy named "FiiCode 2021 Round 2" and there was a task "Clown Fiesta", in a editorial for the task, there were lines such like:
If we take a sequence, where a0=m, a1=φ(a0), a2=φ(a1), ..., ak=1 and m is prime number less than 109, then k will be not greater than log2(m).
Can someone prove it?
P.S link to problem.