According to legend, the three sisters of the Qi family are very mysterious. Not many people have seen them. They are inseparable and wear masks when going out. Only their parents have seen them. Their father said: "They look exactly the same." Their mother said: "The eldest sister has a tear nevus on her left eye, the second sister has a tear nevus on her right eye, and the third sister does not have a tear nevus."
Purpose: Sisters should help each other