PROGRAMMING:Non recursive statistics of the number of right child nodes in binary tree

This problem requires the use of non recursive way to count the number of right child nodes in the binary tree.
###Input format:
Here, the binary tree is established by recursion, and the input sequence is sequenced
###Output format:
The output is the number of the right child nodes of the binary tree
###Input example:
```in
AB@D@@C@@
```
###Output example:
```out
two
```







answer：If there is no answer, please comment