Sure, I can help you create a test case generator for the problem statement you've provided. Let's break down the input format and generate random test cases accordingly.

### Problem Breakdown

1. **Number of Chairs (n)**
   - \(1 \leq n \leq 100\)

2. **Number of Passengers (m)**
   - \(m \leq n\)

3. **Information of the passengers (ai)**
   - Each passenger is represented by a single character from {'A', 'B', 'C', 'D'}.

### Test Case Generator

We'll be generating multiple sets of inputs until we get an input of `0 0`, which indicates the end of the input.

Here is the Python code for the test case generator:

```python
import random

def generate_test_case():
    # Number of chairs (1 ≤ n ≤ 100)
    n = random.randint(1, 100)
    
    # Number of passengers (m ≤ n)
    m = random.randint(1, n)
    
    # Passenger list (m characters from {'A', 'B', 'C', 'D'})
    passengers = [random.choice(['A', 'B', 'C', 'D']) for _ in range(m)]
    
    return n, m, passengers

def generate_multiple_test_cases(num_cases=10):
    test_cases = []
    for _ in range(num_cases):
        n, m, passengers = generate_test_case()
        test_cases.append((n, m, passengers))
    
    return test_cases

def print_test_cases(test_cases):
    for n, m, passengers in test_cases:
        print(f"{n} {m}")
        for passenger in passengers:
            print(passenger)
    print("0 0")

# Generate and print 10 test cases
test_cases = generate_multiple_test_cases(10)
print_test_cases(test_cases)
```

### Explanation

1. **generate_test_case**:
   - Randomly generates the number of chairs `n` (between 1 and 100).
   - Randomly generates the number of passengers `m` (between 1 and `n`).
   - Creates a list of `m` passengers, each represented by a character from {'A', 'B', 'C', 'D'}.

2. **generate_multiple_test_cases**:
   - Calls `generate_test_case` multiple times (default 10) to generate multiple sets of test cases.

3. **print_test_cases**:
   - Prints each test case in the required format.
   - Ends the input with `0 0`.

You can run the script to generate multiple test cases for the problem. Adjust the number of test cases by changing the `num_cases` parameter in `generate_multiple_test_cases` function if needed.