In the following sentence:
Ihr habt lange darauf gewartet.
For the adjective "lange", what is the declination in this case? Here we don't have defined or undefined articles so by the position I would say it should be accusative but then we have two possibilities: feminine and plural (declination with no article). Why should "darauf" be feminine or why should it be plural? Do I need the whole context to be able to point out the gender of what it is meant by "darauf"?