gotoAndPlay problem

programming flash
1

I have a button within a movieClip I setup the button action script as this.

gotoAndPlay(_root.mainmenu, 56);

But I get this error when ever I test it.

Error Symbol=mainmenu-server, layer=Buttons, frame=54:Line 1: Scene name must be quoted string
gotoAndPlay(_root.mainmenu, 56);

Total ActionScript Errors: 1 Reported Errors: 1

Any ideas?