Counting Game

Problem Overview

• Determine the next valid number Zack should call in a counting game with skip rules.
• Given input x (Rose’s call), output -1 if x is invalid; otherwise output the next number not forbidden.
• Numbers are forbidden if they are multiples of 7, contain the digit 7, or are multiples of any number containing 7.
• Real-world context: a casual counting game variant used to test reasoning.
• Trend_micro interview question; a classic coding interview problem for a coding interview.