What is wrong with my if-statement?

I am now trying to explore pascal. And I ran into some compiler errors. I wrote a if else if statement like this:

  if ((input = 'y') or (input = 'Y')) then
    begin
      writeln ('blah blah');
    end;
  else if ((input = 'n') or (input = 'N')) then
    begin
      writeln ('blah');
    end;
  else
    begin
      writeln ('Input invalid!');
    end;

And it gives me an error at the first else:

";" expected but "ELSE" found

I looked for a lot of tutorials about if statements and they just do it like me:

if(boolean_expression 1)then 
   S1 (* Executes when the boolean expression 1 is true *)

else if( boolean_expression 2) then 
   S2 (* Executes when the boolean expression 2 is true *)

else if( boolean_expression 3) then 
   S3 (* Executes when the boolean expression 3 is true *)

else 
   S4; ( * executes when the none of the above condition is true *)

I tried to delete the begin and end but the same error occured. Is this a compiler bug?

P.S. I am doing this in a case statement. But I don't think it matters.