using System;

public class Program

{

    public static void Main()

    {

        Filter("react".ToCharArray());

        Console.WriteLine(FindPeak(new int[] {5, 10, 20, 15}));

    }

    //Find Peak Element

    //Input: array[]= {5, 10, 20, 15}

    //Output: 20

    //O(log n)

    public static int FindPeak(int[] arr)

    {

        return PeakUtil(arr, 0, arr.Length - 1);

    }

    private static int PeakUtil(int[] arr, int l, int h)

    {

        int mid = (l + h) / 2;

        if((mid == 0 || arr[mid] >= arr[mid - 1]) ||

           (mid == arr.Length - 1 || arr[mid] >= arr[mid + 1]))

        {

            return arr[mid];

        }

        if(mid > 0 && arr[mid - 1] > arr[mid])

        {

            return PeakUtil(arr, l, mid-1);

        }

        return PeakUtil(arr, mid + 1, h);

    }

    //Remove b and ac from i/p string

    public static void Filter(char[] charArray)

    {

        int i = -1;

        int j = 0;

        while(j < charArray.Length)

        {

            if(charArray[j] == 'b')

            {

                j++;

            }

            else if(charArray[j] == 'a' && charArray[j+1] == 'c')

            {

                j = j + 2;

            }

            else if(i >=0 && charArray[j] == 'c' && charArray[i] == 'a')

            {

                i = i - 1;

                j = j + 1;

            }

            else

            {

                charArray[++i] = charArray[j++];

            }

        }

         Console.WriteLine(new String(charArray));  

    }

}