One staple food has six choices, and three staple foods have 3×6= 18 (species). The selection of 18 is regarded as 18 drawer, and the students of 124 are regarded as 124 objects, which are evenly distributed to 18 drawer. If 16 students are divided into 18 drawers, there must be a drawer with a score of 6+ 1=7 (name), then at least 7 students buy the same food and staple food.