# Introduction

In Toyland, the trains are always busy delivering treasures across the city, from shiny marbles to rare building blocks.
The tracks they run on are made of colorful domino-shaped pieces, each marked with two numbers.
For the trains to move, the dominoes must form a perfect chain where the numbers match.

Today, an urgent delivery of rare toys is on hold.
You've been handed a set of track pieces to inspect.
If they can form a continuous chain, the train will be on its way, bringing smiles across Toyland.
If not, the set will be discarded, and another will be tried.

The toys are counting on you to solve this puzzle.
Will the dominoes connect the tracks and send the train rolling, or will the set be left behind?
