In the present invention a storage unit (101) stores intervals associated respectively with multiple products. A reception unit (102) receives from a shopper a request specifying, among products purchased by the shopper, a lower-limit product and an upper-limit product. An acquisition unit (103) determines a first retrieval interval, wherein a lower-limit value of a first lower-limit interval associated with the lower-limit product and an upper-limit value of a first upper-limit interval associated with the upper-limit product are set respectively as the lower-limit value and the upper-limit value. A retrieval unit (104) retrieves products associated with an interval overlapping the first retrieval interval. A presentation unit (105) presents to the shopper the products associated with the interval overlapping the first retrieval interval. When a product associated with the interval overlapping the first retrieval interval is stored in the storage unit (101) and the first lower-limit interval and the first upper-limit interval overlap, an updating unit (106) updates the upper-limit value of the first lower-limit interval to a lower value and updates the lower-limit value of the first upper-limit interval to a higher value, so that an overlap interval becomes smaller.