class Solution:
    # @param {integer[]} prices
    # @return {integer}
    def maxProfit(self, prices):
        if len(prices) <= 1:    return 0
        low = prices[0]; mostProfit = 0
        for i in range(1, len(prices)):
            if prices[i] < low: low = prices[i]
            mostProfit = max(mostProfit, prices[i] - low)
        return mostProfit