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_6218 ( "Election date" real, "Party leader" text, "Number of votes received" text, "Percentage of votes" text, "Number of deputies" real )

### Question ###
What was deputies with the lowest number of unknown received votes, in an election year after 1986?

### Accurate SQL ###

SELECT MIN("Number of deputies") FROM table_6218 WHERE "Number of votes received" = 'unknown' AND "Election date" > '1986'