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_17564 ( "Stage" text, "Winner" text, "General classification" text, "Points classification" text, "Mountains classification" text, "Young rider classification" text, "Intergiro classification" text, "Trofeo Fast Team" text )

### Question ###
Who's the winner in stage 1a, where the leader in the young rider classification is Francesco Casagrande?

### Accurate SQL ###

SELECT "Winner" FROM table_17564 WHERE "Young rider classification" = 'Francesco Casagrande' AND "Stage" = '1a'