Joomla Menu and sub menus

Question

I want to display first level of main menu under Joomla. For eg. I have menu something like this

• Heading1
  • Sub-menu1
  • Sub-menu2
  • Sub-menu3
• Heading2
• Heading3

I want to display just Heading1, Heading2, and Heading3 not Sub-menu1,Sub-menu2, and Sub-menu3.

Any help will be appreciated. I've tried using end level and start level but nothing seems to work.

Thanks