user: Question: During which stage was the Intergiro classification held by Miguel Indurain, the Points classification held by Mario Cipollini, and the Young rider classification held by Leonardo Sierra?
Columns: ['Stage', 'Winner', 'General classification', 'Points classification', 'Mountains classification', 'Young rider classification', 'Intergiro classification', 'Trofeo Fast Team']
Types: ['text', 'text', 'text', 'text', 'text', 'text', 'text', 'text']
Sample row: ['1', 'Thierry Marie', 'Thierry Marie', 'Thierry Marie', 'not awarded', 'Julio César Ortegón', 'Miguel Indurain', 'Castorama']
SQL:

assistant: SELECT "Stage" FROM "Table" WHERE "Intergiro classification" = 'Miguel Indurain' AND "Points classification" = 'Mario Cipollini' AND "Young rider classification" = 'Leonardo Sierra';