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_63435 ( "Processor" text, "Model" text, "Clock speed (MHz)" real, "L1 cache (bytes)" text, "Introduced" text, "Discontinued" text )

### Question ###
What is the least clock speed (MHz) with January 1986 as introduced?

### Accurate SQL ###

SELECT MIN("Clock speed (MHz)") FROM table_63435 WHERE "Introduced" = 'january 1986'