Count the number of white papers in image

Hi, What should be the best way to obtain to obtain the number of white papers in a classroom? I've been trying simple methods like binarize, opening, remove small objects and circularities (in some cases it helps). I tried to use hough method but couldn´t figure it out. I though to use superpixel at a starting point. What do you think?

I´m using Matlab 2016b

Thanks