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:
| Series # | Season # | Title | Director | Writer(s) | Original air date |
| --- | --- | --- | --- | --- | --- |
| 15.0 | 1.0 | "The Second Greatest Story Ever Told, Part 1" | John Landis | Marta Kauffman and David Crane | July7,1991 |
| 16.0 | 2.0 | "The Second Greatest Story Ever Told, Part 2" | John Landis | Marta Kauffman and David Crane | July7,1991 |
| 17.0 | 3.0 | "And Your Little Dog, Too" | Catherine O'Hara | Marta Kauffman and David Crane | July14,1991 |
| 18.0 | 4.0 | "The 37-Year Itch" | Betty Thomas | Dava Savel | July21,1991 |
| 19.0 | 5.0 | "Calling the Kettle Black" | Peter Baldwin | Jeff Greenstein and Jeff Strauss | July28,1991 |
| 20.0 | 6.0 | "Futile Attraction" | Arlene Sanford | Marta Kauffman and David Crane | August4,1991 |
| 21.0 | 7.0 | "No, I'm Just Happy to See You" | Arlene Sanford | Jeff Greenstein and Jeff Strauss | August11,1991 |
| 22.0 | 8.0 | "What I Did for Lust" | Bethany Rooney | Theresa Rebeck | August18,1991 |
| 23.0 | 9.0 | "Play Melville for Me" | Arlene Sanford | Craig Hoffman | August25,1991 |
| 24.0 | 10.0 | "To Have and Have and Have and Have Not" | John Axness | Craig Hoffman | September1,1991 |
| 25.0 | 11.0 | "Pants on Fire" | Arlene Sanford | Marta Kauffman and David Crane | September8,1991 |
| 26.0 | 12.0 | "The Charlotte Letter" | Peter Baldwin | Tom Leopold | September15,1991 |
| 27.0 | 13.0 | "The Name of the Game Is Five-Card Stud" | Rob Thompson | Theresa Rebeck | September22,1991 |
| 28.0 | 14.0 | "So Funny I Forgot to Laugh" | Betty Thomas | Jeff Greenstein and Jeff Strauss | September29,1991 |
Question:
When "the 37-year itch" is the title what is the lowest series number?
Answer:
18.0