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 projects ( code text, name text, hours number )
TABLE: CREATE TABLE scientists ( ssn number, name text )
TABLE: CREATE TABLE assignedto ( scientist number, project text )

### Question ###
How many scientists do not have any projects assigned to them?

### Accurate SQL ###

SELECT COUNT(*) FROM scientists WHERE NOT ssn IN (SELECT scientist FROM assignedto)