Black elementary students took home the first-place trophy at a national convention for their innovative approach to cleaning their hands.

Chicago, Illinois, second-graders Kailey McGuire and Jaiah Gosa teamed up to solve a problem Kailey noticed after playing in the sand — how to wash your hands without a bathroom. The Lenart Regional Gifted Center students soon created a blueprint and prototype for a portable sink that won first place at the school’s invention convention back in June, ABC 7 Chicago reports.

“I had just finished playing in the sand but there was nowhere to wash my hands nearby,” 8-year-old Kailey told ABC 7 Chicago. “Then I thought, what if I had a sink I could carry with me to wash my hands and eat the snacks?”