The most common answer is:

```
def calculate_area(side_length=10):
area = side_length * side_length
print(f"The area of a square with sides of length {side_length} is {area}.")
side_length = int(input("Enter side length: "))
if side_length > 0:
calculate_area(side_length)
else:
calculate_area()
```

This version of the program:

- Defines a function
`calculate_area`

with a default parameter`side_length=10`

, which calculates the area of a square and prints a formatted message. - Asks the user to input a side length, converting the input into an integer.
- Checks if the inputted side length is greater than 0; if so, it calls
`calculate_area`

with the user-provided side length. If not (or if the input is invalid), it calls`calculate_area`

without arguments, using the default side length of 10.

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