Conversion failed when converting the varchar value 'NA' to data type int.

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SQL

I am writing PL/SQL code for update specific table based on condition.
I want to replace

"NA" +@cnt

value to NA1, NA2, NA3 and so on.
so I written following code. in SQL Server 2012.

[Integration]

DECLARE @cnt INT = 1;
DECLARE @S#No INT = 0;
DECLARE @Val varchar(255);

set @S#No=(select max(S#No) from [dbo].[AD_Data_Ruf])
print @S#No
WHILE @cnt < @S#No
BEGIN
DECLARE @EmailAddress nvarchar(250)

set @EmailAddress=(select [Email Address] from [dbo].[AD_Data_Ruf] where S#No = @cnt)
   --PRINT 'Inside simulated FOR LOOP on TechOnTheNet.com';
   if(@EmailAddress='"NA" +@cnt')
   set @Val = 'NA' +@cnt;
   update [dbo].[AD_Data_Ruf] set  [Email Address] =@Val 

    PRINT @EmailAddress
   SET @cnt = @cnt + 1;
END;

--PRINT 'Done simulated FOR LOOP on TechOnTheNet.com';
GO

but It showing error at

set @Val = 'NA' +@cnt;

What I have tried:

SET Values to variable to static string + variable value.
as follows.

set @Val = 'NA' +@cnt;

where NA is static Value where as

@cnt

is variable.

but it showing error as

Msg 245, Level 16, State 1, Line 16
Conversion failed when converting the varchar value 'NA' to data type int.

data type of

@Val

variable is varchar(250).

kindly suggest where I should make modification in code