Reorder Routes to Make All Paths Lead to the City Zero

Implement solve for Reorder Routes to Make All Paths Lead to the City Zero. Return the required output for the provided arguments.

Examples
Input: [6,[[0,1],[1,3],[2,3],[4,0],[4,5]]]
Output: 3
Hints

Reorder Routes to Make All Paths Lead to the City Zero

Implement `solve` for **Reorder Routes to Make All Paths Lead to the City Zero**. Return the required output for the provided arguments.