def walk(f, d, numSteps):
    """Assumes: f a Field, d a Drunk in f, and numSteps an int >= 0.
       Moves d numSteps times, and returns the difference between
       the final location and the location at the start of the walk."""
    start = f.getLoc(d)
    for s in range(numSteps):
        f.moveDrunk(d)
    return start.distFrom(f.getLoc(d))