class Solution:
def carFleet(self, target: int, position: List[int], speed: List[int]) -> int:
pair = [[p, s] for p, s in zip(position, speed)]
stack = []
for p, s in sorted(pair)[::-1]:
stack.append((target - p) / s) # how many time need to get to the target
if len(stack) >= 2 and stack[-1] <= stack[-2]:
stack.pop()
return len(stack)
