// Find the maximum possible amount of water in the pool of given profile.

// Overfilled water leaks to the left side of the picture.

// The program reads the sequence of non-negative integer column heights

// until the height -1 that means last column (always having infinite height).

// Then it should output maximum number of cells that could be filled with water.

​

using System;

public class Program

{

    public static void Main()

    {

        Console.WriteLine("Please enter the height of the column.(-1 will be the last column)");

        // Inductive extension:

        int maxColumnHeight = 0;    // Height of highest column entered so far

        int r = 0;                  // Sum of water cells stored so far

        int nextColumnHeight = Convert.ToInt32(Console.ReadLine());

        // invariant: inductive extension holds

        while (nextColumnHeight != -1)

        {

            if (maxColumnHeight < nextColumnHeight)

            {

                maxColumnHeight = nextColumnHeight;

            }

            else

            {

                r += maxColumnHeight - nextColumnHeight;

            }

            nextColumnHeight = Convert.ToInt32(Console.ReadLine());

        }

        // Time complexity: O(n)

​

        Console.WriteLine("Water capacity = " + r);

    }

}