Efficiently Tracking and Querying Word Positions in a List Using a Dictionary

You need to create a program that processes a list of words input by the user, stores the positions (indices) of each word, and then allows querying of these positions. If a user queries a word that exists in the list, the program should return all indices where that word appears. If the word does not exist in the list, it should return "not found." 

1. **Reading Input**:

   - The program starts by taking a single line of input, which consists of words separated by spaces. This line is split into a list of words.

2. **Building Index Dictionary**:

   - The program then constructs a dictionary to map each word to a list of its indices (positions) in the original list. This is achieved by iterating through the list of words and recording each word's position.

3. **Handling Queries**:

   - After building the dictionary, the program waits for another user input, which is a query for a specific word. It looks up this word in the dictionary.

   - If the word exists in the dictionary, it prints out all indices where this word appears. If the word is not found, it outputs "not found."

### Summary:

This approach allows you to efficiently track the positions of words within a list and handle user queries to retrieve these positions. It uses a dictionary to store and quickly access the positions of each word, making it effective for both storing and querying word positions.