MathDB

Given the integer

n\geq 2

and a integer

{a}

, which is coprime with

{n}

. A country has

{n}

islands

D_1

D_2

\cdots

D_n

. For any

1\leq i\neq j\leq n

, there is a one-way ferry

D_i

D_j

if and only if

ij\equiv ia\pmod n

. A tourist can initially fly to any of the islands, and then he can only take a one-way ferry. What is the maximum number of islands he can visit?
Created by Zhenhua Qu

Problem Statement