In a seven - storeyed building, having floors numbered from 1 to 7, A, B, C, D, E, and F each live on a different floor. The ground floor is numbered floor number 1, the floor above it is floor number 2 and so on. One of the floors in the building is vacant. B lives on the floor no.6. No floor below the floor no. 3 is vacant; and no odd numbered floor is vacant. Only B lives between the floors of A and F. Only one person lives between E and D. Only two people live between C and F. C lives on one of the floors below F. More than one person lives between D and B. Which of the following floor numbers is vacant?