package main

// Time: O(n)
// Space: O(1)
func maxProfit(prices []int) int {
	l := len(prices)
	sum, start, last, lock := 0, 0, prices[0], false
	for i := range prices {
		last = prices[i]
		if !lock {
			if i >= l-1 || prices[i+1] > last {
				start = last
				lock = true
			}
		} else {
			if i >= l-1 || prices[i+1] < last {
				sum += last - start
				lock = false
			}
		}
	}
	return sum
}