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:
| Rank | Wrestler | No. of reigns | Combined\ndefenses | Combined\ndays |
| --- | --- | --- | --- | --- |
| 1 | Keiji Mutoh | 4 | 19 | 1,238 |
| 2 | Hiroshi Tanahashi | 6 | 27 | 1,237 |
| 3 | Shinya Hashimoto | 3 | 20 | 1,052 |
| 4 | Tatsumi Fujinami | 6 | 13 | 785 |
| 5 | Kensuke Sasaki | 5 | 9 | 647 |
| 6 | Yuji Nagata | 2 | 12 | 570 |
| 7 | Kazuchika Okada† | 2 | 10 | 556+ |
| 8 | Kazuyuki Fujita | 3 | 3 | 478 |
| 9 | Big Van Vader | 3 | 4 | 451 |
| 10 | Shinsuke Nakamura | 3 | 9 | 390 |
| 11 | Riki Chōshū | 3 | 5 | 383 |
| 12 | Antonio Inoki | 1 | 4 | 325 |
| 13 | Brock Lesnar | 1 | 3 | 280 |
| 14 | Hiroyoshi Tenzan | 4 | 2 | 197 |
| 15 | Yoshihiro Takayama | 1 | 3 | 185 |
| 16 | Satoshi Kojima | 2 | 2 | 168 |
| 17 | Togi Makabe | 1 | 3 | 161 |
| 18 | Scott Norton | 2 | 4 | 126 |
| 19 | Nobuhiko Takada | 1 | 1 | 116 |
| 20 | Bob Sapp | 1 | 1 | 66 |
| 21 | Salman Hashimikov | 1 | 0 | 48 |
| 21 | Tadao Yasuda | 1 | 1 | 48 |
| 23 | Manabu Nakanishi | 1 | 0 | 45 |
| 24 | Masahiro Chono | 1 | 0 | 44 |
| 25 | Genichiro Tenryu | 1 | 0 | 25 |
Question:
what is the difference in combined defenses between hiroshi tanahashi and kensuke sasaki?
Answer:
18