using System;

public class Program

{

    public static void Main()

    {

        Console.WriteLine(Trap(new int[] {0,1,0,2,1,0,1,3,2,1,2,1}));

        Console.WriteLine(Trap(new int[] {4,2,0,3,2,5}));

        Console.WriteLine(Trap(new int[] {4,2,3}));

    }

    public static int Trap(int[] height) {

​

        var lastJ =0;

        int result = 0;

        for(int i = 0; i<height.Length;i++) {

            if (height[i] == 0 || (lastJ > i)) continue;

​

            var maxFromRest = 0;

            var maxJ = 0;

            var nextJ = 0;

            for(int j =i+1; j < height.Length;j++){

                if (height[j]>maxFromRest) {

                    maxFromRest = height[j];

                    maxJ = j;

                }

            }

            for(int j =i+1; j < height.Length;j++){

              if(height[j] >= height[i] || height[j] == maxFromRest) {

                   lastJ = j;

                   var min = Math.Min(height[i], height[j]);

                   var subRes = 0;

                   for(var k = i+1; k<j; k++){

                     if(height[k] <= min) subRes += min - height[k];

                   }

                   result+=subRes;

                   break;

               }

            }

        }

        return result;

}

}