1. An image processing system comprising: a memory storing instructions; and at least one processor configured to execute the instructions to: identify static areas from input images captured at a plurality of time points, wherein, in the static areas, the input images include motion indicating a value smaller than a threshold value; generate a first image using the static areas of respective input images captured in a first time span from a processing time point, a second image using the static areas of respective input images captured in a second time span from the processing time point, and a third image using the static areas of respective input images captured in a third time span from the processing time point; compare the first image and the second image and identify an area having a difference; and classify static objects included in the input images according to a length of a static time period, based on a comparison of the first image, the second image, and the third image.