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:
| Episode # | Original air date (UK) | Episode title | Guest cast | DVD # 1 |
| --- | --- | --- | --- | --- |
| 1-01 | 22 October 1976 | "The Eagle's Nest" | Peter Cushing, Derek Farr, Frank Gatliff, Trevor Baxter, Jerold Wells, Sydney Bromley, Peter Porteous | 1.01 |
| 1-02 | 29 October 1976 | "House of Cards" | Peter Jeffrey, Mark Burns, Annette Andre, Jeremy Wilkin, Frank Thornton, Lyndon Brook, Derek Francis, Gordon Sterne, Anthony Bailey | 1.03 |
| 1-03 | 5 November 1976 | "The Last of the Cybernauts?" | Robert Lang, Oscar Quitak, Basil Hoskins, Robert Gillespie, Gwen Taylor, Ray Armstrong, Martin Fisk | 1.04 |
| 1-04 | 12 November 1976 | "The Midas Touch" | John Carson, Ronald Lacey, Ed Devereaux, Pik-Sen Lim, Geoffrey Bateman, Tim Condren, Chris Tranchell, David Swift | 1.02 |
| 1-05 | 19 November 1976 | "Cat Amongst the Pigeons" | Vladek Sheybal, Basil Dignam, Paul Copley, Kevin Stoney, Hugh Walters, Brian Jackson, Gordon Rollings | 1.06 |
| 1-06 | 26 November 1976 | "Target" | Keith Barron, Frederick Jaeger, Robert Beatty, Bruce Purchase, Roy Boyd, Deep Roy, John Paul, Malcolm Stoddard | 1.07 |
| 1-07 | 3 December 1976 | "To Catch a Rat" | Ian Hendry, Barry Jackson, Edward Judd, Dallas Cavell, Jo Kendall | 1.05 |
| 1-08 | 10 December 1976 | "The Tale of the Big Why" | Derek Waring, Jenny Runacre, Roy Marsden, George A. Cooper, Geoffrey Toone, Gary Waldhorn | 1.09 |
| 1-09 | 17 December 1976 | "Faces" | David de Keyser, Edward Petherbridge, Richard Leech, Michael Sheard, Donald Hewlett, Neil Hallett, David Webb, J. G. Devlin | 1.08 |
| 1–10 | 21 December 1976 | "Gnaws" | Julian Holloway, Peter Cellier, Jeremy Young, Patrick Malahide, W. Morgan Sheppard, Keith Marsh | 1.11 |
| 1–11 | 7 January 1977 | "Dirtier by the Dozen" | John Castle, Shaun Curry, Alun Armstrong, Michael Barrington, Brian Croucher, Stephen Moore, John Forbes-Robertson, David Purcell | 1.13 |
| 1–12 | 14 January 1977 | "Sleeper" | Keith Buckley, Sara Kestelman, Prentis Hancock, Mark Jones | 1.12 |
| 1–13 | 21 January 1977 | "Three-Handed Game" | Stephen Greif, Tony Vogel, David Wood, Ronald Leigh-Hunt, Annie Lambert, Hugh Morton, John Paul | 1.10 |
Question:
what is the least number of guest casts on an episode?
Answer:
4