Please read the following table in Markdown format and then answer the question according to the table. Table cells in one row are seperated by '|', and different rows are seperated by '
'.

Table:
| Year | Entrant | Chassis | Engine | Points |
| --- | --- | --- | --- | --- |
| 1955.0 | Scuderia Volpini | Arzani-Volpini | Maserati Straight-4 | 0.0 |
| 1956.0 | Officine Alfieri Maserati | Maserati 250F | Maserati Straight-6 | 0.0 |
| 1956.0 | Luigi Piotti | Maserati 250F | Maserati Straight-6 | 0.0 |
| 1957.0 | Luigi Piotti | Maserati 250F | Maserati Straight-6 | 0.0 |
| 1958.0 | Automobili OSCA | O.S.C.A | O.S.C.A Straight-4 | 0.0 |
Question:
Name the engine with chassis of maserati 250f and entrant of luigi piotti with year less than 1957
Answer:
Maserati Straight-6