using System;

public class Program

{

    public static void Main()

    {

        var test = "[XR] Z_Prem_4000+_Delphi_700+ [InstalmentScheme 1]";

        Console.WriteLine(Extract(test));

        test = "[XR] Z_Prem_4000+_Delphi_700+ [InstalmentScheme 26]";

        Console.WriteLine(Extract(test));

        test = "[XR] Z_Prem_4000+_Delphi_700+ [InstalmentScheme ]";

        Console.WriteLine(Extract(test));

    }

    public static int Extract( ReadOnlySpan<char> input )

    {

        var lastIndex = input.LastIndexOf(' ');

        if (lastIndex < 0) return 0;

        return int.TryParse(input[lastIndex..^1], out int result) ? result : 0;

    }

}