def max_sum_slice(xs):
best_sum, best_start, best_end = 0, None, None
for i, x in enumerate(xs):
if best_start is None or best_sum < x + best_sum:
best_sum = x + best_sum
best_start = i
best_end = i
elif best_sum > x + best_sum:
best_sum = x + best_sum
best_end = i
return best_sum, best_start, best_end