Binary Tree Path Sum

Given a binary tree represented in level-order (breadth-first traversal), determine whether there exists a path from the root to a leaf such that the sum of the node values equals a given target sum. Formally, you need to decide if there exists a path satisfying $$\sum_{node\in path}{node.val} = target\_sum$$.

The binary tree may contain missing nodes which are indicated by the keyword null.

inputFormat

The input is read from standard input and consists of three parts:

1. The first line contains an integer n, representing the number of tokens (node values) provided in level-order.
2. The second line contains n tokens separated by spaces. Each token is either an integer or the string null, which represents a missing node.
3. The third line contains an integer representing the target sum.

outputFormat

Output a single line to standard output: YES if there exists a root-to-leaf path whose node values sum to the target sum, otherwise output NO.

## sample

5
5 4 8 11 13
22

YES

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