Let's consider the function `mystery` and evaluate it step by step for the input value of 4. The function is defined recursively, and here's the process it follows:
1. Step 1: Call mystery(4)
- Since 4 is not less than or equal to 1, we move to the else part.
- This means we need to calculate `4 mystery(4 - 1)`, which is `4 mystery(3)`.
2. Step 2: Call mystery(3)
- Similarly, since 3 is not less than or equal to 1, we need to calculate `3 mystery(3 - 1)`, which is `3 mystery(2)`.
3. Step 3: Call mystery(2)
- As 2 is still not less than or equal to 1, we proceed to calculate `2 mystery(2 - 1)`, which is `2 mystery(1)`.
4. Step 4: Call mystery(1)
- Here, 1 is equal to 1, so according to the function, it returns 1.
Now, let's compile the results of these recursive calls:
- From Step 4, `mystery(1)` returns 1.
- From Step 3, this means `mystery(2)` returns `2 1 = 2`.
- From Step 2, `mystery(3)` returns `3 2 = 6`.
- From Step 1, `mystery(4)` returns `4 * 6 = 24`.
Thus, the function `mystery` returns the value 24 when called with an input of 4.
