```python
from typing import List

def pace_of(seconds: int, kilometres: int) -> int:
    if kilometres <= 0:
        raise ValueError("Distance must be positive")
    return seconds // kilometres

def pace_list(legs: list) -> list:
    if not legs:
        raise ValueError("No legs provided")
    
    for leg in legs:
        if leg[1] > 0:
            yield pace_of(*leg)
        else:
            raise ValueError(f"Leg covering no ground: {leg}")
```