Below is the list of tables from the database along with their columns and datatype. Need to generate an accurate SQL query for the question.
Only use the columns present in the respective table. Only use the columns which are required to generate the SQL query. Only use table joins if required and not otherwise.

### Tables ###
TABLE: CREATE TABLE table_4937 ( "Name" text, "Vertices V" real, "Edges E" real, "Faces F" real, "Euler characteristic: V \u2212 E + F" real )

### 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?

### Accurate SQL ###

SELECT MIN("Euler characteristic: V \u2212 E + F") FROM table_4937 WHERE "Faces F" < '20' AND "Edges E" < '30' AND "Name" = 'hexahedron or cube' AND "Vertices V" < '8'