what is the minimum stage where mountains classification is aitor osa and aitor gonz lez won?
CREATE TABLE table_15088557_1 (
    stage INTEGER,
    mountains_classification VARCHAR,
    winner VARCHAR
)
SELECT MIN(stage) FROM table_15088557_1 WHERE mountains_classification = "Aitor Osa" AND winner = "Aitor González"
Below are sql tables schemas paired with instruction that describes a task. Using valid SQLite, write a response that appropriately completes the request for the provided tables. ### Instruction: what is the minimum stage where mountains classification is aitor osa and aitor gonz lez won? ### Input: CREATE TABLE table_15088557_1 (
    stage INTEGER,
    mountains_classification VARCHAR,
    winner VARCHAR
) ### Response: SELECT MIN(stage) FROM table_15088557_1 WHERE mountains_classification = "Aitor Osa" AND winner = "Aitor González"