sql insert query error

CREATE TABLE [dbo].[tb_mst_Attachement](
    [MessageId_int] [int] NULL,
    [Document_nvarchar] [nvarchar](50) ,
    [ImagePath] [nvarchar](max)
)


CREATE TABLE [dbo].[tb_mst_Message](
    [MessageId_int] [int] IDENTITY(1,1) NOT NULL,
    [Subject_nvarchar] [nvarchar](max) COLLATE Latin1_General_CI_AI NULL,
    [Message_nvarchar] [nvarchar](max) COLLATE Latin1_General_CI_AI NULL,
    [IsAttachment] [int] NULL,
)


insert into tb_mst_Message ( SenderId_int, ReceiverId_int, Subject_nvarchar )values (101,202,'hii')

insert into tb_mst_Attachement values((select max(MessageId_int) from tb_mst_Message),'hi','how r u')