------
## 最终结论
```python
def choose_num(x, y):
    """This function takes two positive numbers x and y and returns the
    biggest even integer number that is in the range [x, y] inclusive. If 
    there's no such number, then the function should return -1.
    """
    if x <= 0 or y <= 0:
        return -1  # Ensure both numbers are positive
    if x > y:
        x, y = y, x  # Swap if x is greater than y
    
    # Find the largest even number in the range
    for num in range(y, x - 1, -1):
        if num % 2 == 0:
            return num
    
    return -1
```