using System;

/* You are given an array prices where prices[i] is the price of a given stock on the ith day.

​

You want to maximize your profit by choosing a single day to buy one stock and choosing a different day in the future to sell that stock.

​

Return the maximum profit you can achieve from this transaction. If you cannot achieve any profit, return 0. 

​

[7,1,5,3,6,4]

​

*/

​

public class Program

{

    public int MaxProfit(int[] prices) {

        int smallestStockPrice = prices[0];

        int profit = 0;

        for(int i = 1; i < prices.Length; i++)

        {

            if(prices[i] < smallestStockPrice)

            {

                smallestStockPrice = prices[i];

            }

            else

            {

                profit = Math.Max(profit, prices[i] - smallestStockPrice);

            }

        }

        return profit;

    }

    public static void Main()

    {

        Program output = new Program();

        int[] input = {7,1,5,3,6,4};

        Console.WriteLine(output.MaxProfit(input));

    }

}