gdal_merge.py not working after gdal and it python bindings have been installed

I installed Python 3.4.0 64 bit and gdal file release-1400-x64-gdal-1-11-1-mapserver-6-4-1.zip from http://ift.tt/1EbvBCh. I found the binding from http://ift.tt/1jTmHBw and the filename is GDAL-1.11.2-cp34-none-win_amd64. I successfully install these files and import gdal. However, when I run the following command within the Python IDE to merge files 1 2 and 3, I got an error

 >>> gdal_merge.py -o out.tif 1.tif 2.tif 3.tif
  File "<console>", line 1
   gdal_merge.py -o out.tif 1.tif 2.tif 3.tif
                   ^
 SyntaxError: invalid syntax

I specifically check to see if I can import gdal_merge as below

>>> import gdal_merge

and it was ok. I appreciate if anybody could help with this issue.