using System;

public class Program

{

    public static void Main()

    {

      int [] arr = new int[] {3,7,9,12,15};

      Console.WriteLine(IsSort(arr));

    } 

    public static bool IsSort(int []arr)

    {

     for (int i=0 ; i<arr.Length-1 ; i++)

     {

        if (arr[i] == arr[i+1]) 

        return false;

     }

        return true;

    }

}