Car Fleet

def carFleet(target, position, speed):
    pair = [[p, s] for p, s in zip(position, speed)]
    stack = []
    
    for p, s in sorted(pair)[::-1]: # Reverse sorted order
        stack.append((target - p) / s)
        if len(stack) >= 2 and stack[-1] <= stack[-2]:
            stack.pop()
            
    return len(stack)