user: Question: What is the lowest Euler characteristic: V-E+F of a hexahedron or cube, which has less than 20 faces F, less than 30 edges E, and less than 8 vertices V?
Columns: ['Name', 'Vertices V', 'Edges E', 'Faces F', 'Euler characteristic: V − E + F']
Types: ['text', 'real', 'real', 'real', 'real']
Sample row: ['Tetrahedron', 4.0, 6.0, 4.0, 2.0]
SQL:

assistant: SELECT MIN("Euler characteristic: V − E + F") FROM "Table" WHERE "Faces F" < 20.0 AND "Edges E" < 30.0 AND "Name" = 'hexahedron or cube' AND "Vertices V" < 8.0;