Uber generates ride identifiers that must follow strict compliance and formatting constraints due to regional regulations and internal validation rules. Given an integer n and a set of allowed_digits of size k, find the ride identifier representing the smallest positive integer such that:

• The ride identifier is a multiple of n
• Each digit of the ride identifier must be present in allowed_digits
• No two consecutive digits in the ride identifier are equal

Return a string ride identifier if it satisfies all the conditions. If no such ride identifier exists, return '-1' as a string.