leerlingenInformatica =
{"Sander (423766)", "Sander (429102)", "Lennart (424911)", "Ewout (423141)", "Lotte (425926)", "Noëlle (425358)", "Sofie (429793)", "Niels (422311)"}
leerlingenFrans =
{"Friso (429182)", "Sander (423766)", "Paul (427102", "Elise (424019", "Lennart (424911)", "Jelle (420192)", "Jaïra (421421)", "Peter (427108"}
doorsnede = leerlingenInformatica.intersection(leerlingenFrans)
print(doorsnede)