Certainly! To create a test case generator for the given problem statement, we need to generate random values for \(X\) and \(Y\) such that \(1 \leq X \leq Y \leq 10^{18}\). Here is a Python function to generate such test cases:

```python
import random

def tcgen():
    X = random.randint(1, 10**18)
    Y = random.randint(X, 10**18)
    
    return X, Y

# Example usage
for _ in range(5):
    print(tcgen())
```

This function will generate random pairs of integers \(X\) and \(Y\) that satisfy the constraints given in the problem statement. Here is a brief explanation:

1. **X** is chosen randomly between 1 and \(10^{18}\) (inclusive).
2. **Y** is chosen randomly between \(X\) and \(10^{18}\) (inclusive), ensuring that \(X \leq Y\).

This test case generator ensures that the constraints \(1 \leq X \leq Y \leq 10^{18}\) are always met, providing valid inputs for the problem.