const maxProfit = prices => {
  let profit = 0;
  let start = 0,
    end = 0;

  // sum of all ascendent subsequences
  for (let i = 1; i < prices.length; i++) {
    if (prices[i] > prices[i - 1]) {
      end = i;
    } else {
      profit += prices[end] - prices[start];
      start = i;
      end = i;
    }
  }

  if (end === prices.length - 1) profit += prices[end] - prices[start];

  return profit;
};