Count Leaf Nodes

Easyjavapythonccppjavascript

Count the number of nodes in a binary tree that have no children.

Input Format

The first line contains an integer M, the number of level-order tokens. The second line contains M space-separated tokens (integers or null). It is blank when M is 0.

Output Format

Print the number of leaf nodes.

Example 1

Input

5
1 2 3 4 5

Output

Explanation: Nodes 4, 5 and 3 are leaves.

Input (stdin)

Output

Run your code to see output here...