Given the root node root of a binary tree where each node contains a single digit, treat every root to leaf path as a base $10$ number formed by concatenating the digits along that path from root to leaf.

Return the sum of all such numbers across every root to leaf path in the tree.

A leaf is a node with no children.

Constraints:

• The number of nodes in the tree is in the range $[1, 1000]$

• $0 \leq$ Node.val $\leq 9$

• The depth of the tree will not exceed $10$

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