You're given a string of dominos. For each slot, there are 3 options:
  * "|" represents a standing domino
  * "/" represents a knocked over domino
  * " " represents a space where there is no domino
For example: 
```python
"||| ||||//| |/"
```
What you must do is find the resulting string if the first domino is pushed over. Now, tipping a domino will cause the next domino to its right to fall over as well, but if a domino is already tipped over, or there is a domino missing, the reaction will stop.
So in out example above, the result would be:
"/// ||||//| |/"
since the reaction would stop as soon as it gets to a space.
def domino_reaction(s):
    ds = ""
    for (i,d) in enumerate(s):
        if( d=="|" ): 
            ds += "/"
        else:
            return ds+s[i:]
    return ds

def domino_reaction(s):
    ds = ""
    for (i,d) in enumerate(s):
        if( d=="|" ): 
            ds += "/"
        else:
            return ds+s[i:]
    return ds
