using System;

​

public class Program

{

    // Given sorted array "arr" and a number "x" find the index at which "x" is present in the array using binary search.

    // If "x" is not present in the array, return -1.

    static int BinarySearch(int[] arr, int x)

    {

        return -1;

    }

    public static void VerifyNumberPresence(int[] arr, int x)

    {

        int result = BinarySearch(arr, x);

        if (result == -1)

        {

            Console.WriteLine($"Number {x} is not present in array");

        }

        else

        {

            Console.WriteLine($"Number {x} is present at index {result}");

        }

    }

    public static void Main()

    {

        int[] arr = { 2, 3, 4, 15, 50 };

        foreach(int num in arr)

        {

            VerifyNumberPresence(arr, num);

        }

        VerifyNumberPresence(arr, 51);

        VerifyNumberPresence(arr, 1);

        VerifyNumberPresence(arr, 5);

        VerifyNumberPresence(arr, 11);

    }

​

}