```python
def steps_on(first: int, count: int) -> list:
    """Return a list of 'count' consecutive integers starting from 'first'."""
    if count < 0:
        raise ValueError("count must be non-negative")
    return list(range(first, first + count))


def hole_find(seen: list, first: int, count: int) -> int:
    """Return the first missing integer in the expected sequence, or -1 if none."""
    expected = set(steps_on(first, count))
    seen_set = set(seen)
    for num in sorted(expected):
        if num not in seen_set:
            return num
    return -1
```